IVOAT Thesaurus - Version Mon Jun 2 18:20:55 2008
type: ConceptScheme
has top concept: Doppler effect
has top concept: Fourier transform
has top concept: Julian Date
has top concept: Kapteyn selected area
has top concept: Newtonian telescope
has top concept: X-ray spectrum
has top concept: absorption
has top concept: abundance
has top concept: active region
has top concept: almanac
has top concept: analysis
has top concept: anomaly
has top concept: arc
has top concept: array
has top concept: artificial satellite
has top concept: astronomical research
has top concept: astronomical technique
has top concept: atlas
has top concept: atmosphere
has top concept: atmospheric radiation
has top concept: binary system
has top concept: blue object
has top concept: bubble
has top concept: bulge
has top concept: burst
has top concept: calendar
has top concept: calibration
has top concept: catalog
has top concept: chemical element
has top concept: chemical evolution
has top concept: classification
has top concept: cloud
has top concept: cluster
has top concept: coating
has top concept: coherence
has top concept: collapse
has top concept: collision process
has top concept: compact object
has top concept: computer
has top concept: computing
has top concept: constant
has top concept: control system
has top concept: coordinate system
has top concept: corona
has top concept: correlation
has top concept: crater
has top concept: density
has top concept: design
has top concept: detection
has top concept: diffraction
has top concept: dimension
has top concept: dipole
has top concept: disk
has top concept: distance measurement
has top concept: distance scale
has top concept: eclipse
has top concept: electrode
has top concept: electrodynamics
has top concept: electromagnetic theory
has top concept: electron beam
has top concept: electronic camera
has top concept: electronic equipment
has top concept: emission line object
has top concept: encounter
has top concept: energy
has top concept: energy-transfer
has top concept: epoch
has top concept: equinox
has top concept: error
has top concept: evolution
has top concept: evolutionary track
has top concept: extragalactic object
has top concept: eyepiece
has top concept: filter
has top concept: fission
has top concept: flare
has top concept: flow
has top concept: fluorescence

21-cm line
type: Concept
alternative label: 21 cm line
broader: radio recombination line
definition: 21 centimeter line of hydrogen
related: H I
related: H I absorption
related: H I cloud
related: H I content
related: H I emission
related: H I region
related: hydrogen
related: radio frequency

53 Persei star
type: Concept
broader: B star
broader: pulsating variable star
definition: 53 Persei star

Abell cluster
type: Concept
broader: galaxy cluster
definition: Abell cluster

aberration
type: Concept
definition: aberration of light
related: astrometry
related: coordinate system

ablation
type: Concept
definition: ablation
related: meteorite

abnormal spectrum
type: Concept
broader: spectrum
definition: abnormal spectrum
related: peculiar star

absolute magnitude
type: Concept
broader: magnitude
definition: absolute magnitude
related: Hertzsprung-Russell diagram
related: Wilson-Bappu effect
related: distance
related: distance modulus
related: luminosity

absolute temperature scale
type: Concept
broader: temperature scale
definition: absolute temperature scale
narrower: Kelvin
related: celsius temperature scale
related: temperature
scope note: ES: moved Kelvin from RT to NT (2007-OCT-8)

absorption
type: Concept
definition: absorption
narrower: atmospheric extinction
narrower: intergalactic absorption
narrower: interstellar absorption
narrower: light absorption
related: Rosseland opacity
related: atmospheric scattering
related: atmospheric window
related: capture
related: equivalent width
related: interstellar gas
related: opacity
related: photodissociation
related: photoionization
related: radiation
related: radiative equilibrium
related: reddened star
related: reddening
related: transmission
scope note: combine with other terms

absorption coefficient
type: Concept
alternative label: absorptivity
definition: absorption coefficient
related: Einstein coefficient
related: atmospheric extinction
related: intergalactic absorption
related: interstellar absorption
related: optical depth
related: transparency

absorption line
type: Concept
broader: spectral line
definition: absorption line
narrower: absorption line system
related: Lyman alpha forest
related: Voigt profile
related: atomic process
related: bound-free transition
related: calcium line
related: cyanogen line
related: line formation
related: line identification
related: line profile
related: line ratio
related: metal line
related: microturbulence
related: residual intensity
related: spectroscopic analysis
related: spectrum

absorption line system
type: Concept
broader: absorption line
broader: system
definition: absorption line system
history note: ES: new (2007-OCT-8)
related: quasar

absorption spectroscopy
type: Concept
broader: spectroscopy
definition: absorption spectroscopy

absorption spectrum
type: Concept
broader: line spectrum
broader: spectrum
definition: absorption spectrum
narrower: atomic spectrum
related: Balmer series
related: D line
related: Fraunhofer line
related: Raman effect
related: bound-free transition
related: energy spectrum

abundance
type: Concept
alternative label: chemical abundance
alternative label: element abundance
alternative label: stellar abundance
definition: abundance
narrower: cosmic abundance
narrower: isotopic abundance
narrower: metal abundance
narrower: overabundance
narrower: underabundance
related: CNO anomaly
related: abundance ratio
related: chemical composition
related: chemical element
related: chemical evolution
related: curve of growth
related: element formation
related: enrichment
related: heavy element
related: helium-poor star
related: helium-rich star
related: peculiar star
related: rare earth
scope note: may be combined with element, e.g. helium abundance

abundance ratio
type: Concept
definition: abundance ratio
related: CNO anomaly
related: abundance

acceleration
type: Concept
broader: kinematics
definition: acceleration
related: deceleration
related: gravimetry
related: orbit
related: orbital element

accretion
type: Concept
definition: accretion
related: Alfven surface
related: accretion disk
related: binary star
related: mass-transfer
related: particle accretion

accretion disk
type: Concept
broader: disk
definition: accretion discs UK
definition: accretion disk
related: accretion
related: black hole
related: circumstellar disk
related: close binary star
related: cooling flow
related: dwarf nova
related: low-mass X-ray binary star
related: stellar wind
related: superhump

achondrite
type: Concept
broader: chondrite
broader: meteorite
definition: achondrite

acoustics
type: Concept
definition: acoustics
related: acoustic wave

acoustic wave
type: Concept
alternative label: sound
alternative label: sound wave
broader: wave
definition: acoustic wave
related: acoustics
related: gravity wave
related: sound speed
related: wavelength

actinium
type: Concept
alternative label: Ac
broader: fundamental chemical element
definition: actinium (atomic number 89)
history note: FVH: new (2007-OCT-25)

active galactic nucleus
type: Concept
alternative label: AGN
broader: X-ray source
broader: galactic nucleus
broader: variable source
definition: active galactic nucleus
narrower: Seyfert nucleus
narrower: blazar
related: BL Lacertae object
related: active galaxy
related: compact nucleus
related: emission line galaxy
related: galaxy
related: quasar
related: radio galaxy

active galaxy
type: Concept
alternative label: eruptive galaxy
broader: X-ray source
broader: galaxy
definition: active galaxy
related: X-ray flare
related: active galactic nucleus
related: compact galaxy
related: emission line galaxy

active optics
type: Concept
broader: optics
definition: active optics
related: adaptive optics
related: atmospheric refraction
related: multiple mirror telescope
related: seeing
related: tip-tilt mirror

active prominence
type: Concept
broader: active region
broader: prominence
definition: active prominence
related: Sun

active region
type: Concept
definition: solar active region
history note: FVH: new (2007-OCT-29)
narrower: active prominence
related: Sun

active star
type: Concept
broader: star
definition: active star
narrower: X-ray star
narrower: emission line star
related: X-ray flare

active Sun
type: Concept
broader: Sun
definition: active Sun
related: flare
related: quiet Sun
related: solar activity
related: solar cycle
related: sunspot

activity index
type: Concept
definition: activity index
related: solar activity

adaption
type: Concept
definition: adaption
scope note: combine with other terms

adaptive optics
type: Concept
broader: optics
definition: adaptive optics
related: active optics
related: atmospheric refraction
related: seeing
related: segmented optics

adiabatic process
type: Concept
definition: adiabatic process
related: energy-transfer
related: thermodynamics

adjustment
type: Concept
definition: adjustment
related: alignment optics
related: collimation
related: correction
related: optics
related: orientation
scope note: combine with other terms

adsorption
type: Concept
definition: adsorption
related: dust grain
related: interplanetary grain
related: interstellar dust
scope note: combine with other terms

A dwarf
type: Concept
broader: A star
broader: dwarf
definition: A dwarf star
related: A subdwarf

aerolite
type: Concept
broader: meteorite
definition: aerolite

aeronomy
type: Concept
broader: scientific field
definition: aeronomy
related: Earth atmosphere
related: atmosphere
related: planet

Ae star
type: Concept
broader: A star
broader: Herbig AeBe star
broader: early-type emission star
definition: Ae star
narrower: Herbig AeBe star
related: Be star

afterglow
type: Concept
broader: atmospheric radiation
definition: afterglow
related: light scattering
related: luminescence

age
type: Concept
definition: age
related: Hubble time
related: cosmochronology
related: relaxation time
related: turnoff point
scope note: combine with other terms

A giant
type: Concept
broader: A star
broader: giant
definition: A giant star

air
type: Concept
broader: gas
definition: air
related: atmosphere

air conditioning
type: Concept
definition: air conditioning
related: temperature control
related: ventilation

airglow
type: Concept
alternative label: dayglow
alternative label: nightglow
broader: atmospheric radiation
definition: airglow
related: Rayleigh scattering
related: ashen light
related: aurora
related: night sky brightness
related: radiative recombination
related: sky brightness

airplane-borne instrument
type: Concept
alternative label: airplane borne instrument
broader: instrument
definition: airplane-borne instrument
related: balloon-borne instrument
related: ground-based astronomy
related: infrared observatory
related: rocket-borne instrument
related: satellite-borne instrument

air pollution
type: Concept
broader: pollution
definition: air pollution
related: light pollution
related: site protection

Airy disk
type: Concept
definition: Airy discs UK
definition: Airy disk
related: diffraction

albedo
type: Concept
alternative label: spherical albedo
broader: optical property
definition: albedo
related: illumination
related: radiation
related: reflection
related: surface property

Alfven surface
type: Concept
definition: Alfven surface
related: accretion
related: neutron star

Alfven wave
type: Concept
alternative label: hydromagnetic wave
broader: magnetohydrodynamics
definition: Alfven wave
narrower: coronal wave

Algol variable star
type: Concept
alternative label: beta Persei star
broader: binary star
broader: eclipsing binary star
definition: Algol variable star
related: W Ursae Majoris star

alignment optics
type: Concept
definition: alignment of optical image
related: adjustment
related: collimation
related: correction
related: orientation

all-sky camera
type: Concept
alternative label: all sky camera
broader: camera
broader: wide-field telescope
change note: FVH: added NT CLOUD_MONITORS (2007-SEP-21)
definition: all-sky camera
narrower: cloud monitor
related: all-sky photography
related: wide-angle lens

all-sky photography
type: Concept
alternative label: all sky photography
broader: photography
definition: all-sky photography
related: all-sky camera
related: camera
related: wide-angle lens

almanac
type: Concept
definition: almanac
narrower: nautical almanac
related: ephemeris

alpha2 Canum Venaticorum star
type: Concept
broader: eruptive binary star
broader: magnetic variable star
change note: FVH: removed incorrect BT cataclysmic_variable_star (2007-OCT-2)
definition: alpha2 Canum Venaticorum star
related: Ap star
related: SX Arietis star
related: spectrum variable star

alpha particle
type: Concept
broader: boson
broader: composite particle
broader: nuclear radiation
broader: particle
definition: alpha particle
related: electron
related: neutron
related: proton
related: radioactivity

altazimuth mounting
type: Concept
alternative label: alt-azimuth mounting
alternative label: azimuth mounting
broader: telescope mounting
definition: altazimuth mounting
related: altitude angle
related: azimuth
related: equatorial mounting
related: horizon coordinate system
related: siderostat
related: vertical circle

altimeter
type: Concept
broader: measuring instrument
definition: altimeter
related: weather station

altimetry
type: Concept
definition: altimetry

altitude angle
type: Concept
alternative label: elevation angle
definition: altitude [angle]
related: altazimuth mounting
related: azimuth
related: horizon
related: horizon coordinate system
related: sextant
related: zenith distance
scope note: use for angle; see ALTITUDE_HEIGHT for height

aluminizing
type: Concept
definition: aluminizing
related: aluminum coating
related: mirror
related: vacuum technique

aluminum
type: Concept
alternative label: Al
broader: fundamental chemical element
definition: aluminum (atomic number 13)
history note: FVH: new (2007-OCT-25)
narrower: aluminum coating

aluminum coating
type: Concept
broader: aluminum
broader: coating
broader: thin film
change note: FVH: moved aluminium_coating to localized D (2007-SEP-24)
definition: aluminium coating UK
definition: aluminum coating
related: aluminizing
related: mirror
related: optical surface
related: silver coating
related: vacuum technique
related: vapor deposition

amateur astronomy
type: Concept
broader: astronomy
definition: amateur astronomy
related: astronomer
related: astronomical research

AM Canum Venaticorum star
type: Concept
broader: hydrogen deficient star
broader: nova-like variable
definition: AM Canum Venaticorum star
related: UX Ursae Majoris star
related: dwarf nova

americium
type: Concept
alternative label: Am
broader: fundamental chemical element
definition: americium (atomic number 95)
history note: FVH: new (2007-OCT-25)

AM Herculis star
type: Concept
alternative label: polars
broader: cataclysmic variable star
definition: AM Herculis star

ammonia
type: Concept
broader: interstellar molecule
definition: ammonia

Amor group
type: Concept
broader: minor planet family
definition: Amor group
related: Apollo group
related: Trojan group

amplifier
type: Concept
broader: instrument
definition: amplifier
narrower: microchannel plate
narrower: parametric amplifier
narrower: preamplifier
related: image tube
related: photomultiplier tube
related: pulse counter
related: pulse counting

amplitude
type: Concept
definition: amplitude
related: decay oscillation
related: magnitude
related: oscillation
related: pulsation
related: variable star
related: vibration

Am star
type: Concept
broader: A star
broader: magnetic star
broader: magnetic variable star
broader: metal-rich star
definition: Am star
narrower: spectrum variable star

analog recorder
type: Concept
broader: data storage
definition: analog recorder

analysis
type: Concept
definition: analysis
narrower: data analysis
narrower: fine analysis
narrower: signal analysis
narrower: signal processing
related: astronomical technique
related: quantization
related: reduction method
scope note: combine with other terms

anemometer
type: Concept
broader: measuring instrument
definition: anemometer
history note: FVH: new (2007-SEP-21)
related: weather station
related: wind vane

angular diameter
type: Concept
alternative label: apparent diameter
broader: diameter
definition: angular diameter
narrower: isophotal diameter
related: interferometry
related: occultation
related: speckle interferometry

angular momentum
type: Concept
definition: angular momentum
related: kinematics
related: momentum
related: rotation

angular resolution
type: Concept
broader: resolution
definition: angular resolution
related: angular separation
related: beamwidth
related: optics
related: speckle interferometry

angular separation
type: Concept
alternative label: angular distance
definition: angular separation
related: angular resolution
related: optical double star
related: speckle interferometry

angular velocity
type: Concept
broader: velocity
definition: angular velocity
related: celestial mechanics
related: orbital velocity
related: rotation

anisotropy
type: Concept
definition: anisotropy
related: background radiation
related: isotropy
related: polarization charge separation

annual equation
type: Concept
definition: annual equation
related: Earth-Moon system
related: Earth orbit
related: elliptical orbit

annual parallax
type: Concept
alternative label: heliocentric parallax
alternative label: parallax
broader: parallax
definition: annual parallax
related: Astronomical Unit

annular eclipse
type: Concept
broader: eclipse
definition: annular eclipse
related: total eclipse

anomalistic month
type: Concept
definition: anomalistic month
related: Moon
related: orbital anomaly

anomalistic year
type: Concept
broader: year
definition: anomalistic year
related: orbital anomaly

anomaly
type: Concept
change note: FVH: generic non-orbital anomaly; old entry moved to orbital_anomaly (2007-OCT-29)
definition: anomaly
narrower: CNO anomaly
narrower: gravity anomaly
narrower: magnetic anomaly

ansa
type: Concept
definition: ansa
related: lenticular galaxy
related: planetary nebula
related: ring

antapex
type: Concept
definition: antapex
related: apex
related: solar motion

antarctic observatory
type: Concept
broader: observatory
definition: antarctic observatory

antenna
type: Concept
alternative label: aerials
alternative label: antennas
broader: radar equipment
definition: antenna
narrower: Cassegrain antenna
narrower: Mills cross antenna
narrower: Yagi antenna
narrower: dipole antenna
narrower: directional antenna
narrower: horn antenna
narrower: lens antenna
narrower: microwave antenna
narrower: parabolic antenna
narrower: radio antenna
narrower: reflector antenna
related: array
related: current
related: current sheet
related: dish antenna
related: feed horn
related: interferometer
related: radar
related: radio telescope
related: telescope

antenna design
type: Concept
definition: antenna design
related: polar diagram
related: radio telescope

anthropic principle
type: Concept
definition: anthropic principle
related: cosmology
related: life

antimatter
type: Concept
broader: matter
definition: antimatter
narrower: antiparticle

antimony
type: Concept
alternative label: Sb
broader: fundamental chemical element
definition: antimony (atomic number 51)
history note: FVH: new (2007-OCT-25)

antineutrino
type: Concept
broader: antiparticle
definition: antineutrino
related: neutrino

antinode
type: Concept
definition: antinode
related: vibration

antinucleon
type: Concept
broader: antiparticle
definition: antinucleon

antiparticle
type: Concept
broader: antimatter
broader: elementary particle
definition: antiparticle
narrower: antineutrino
narrower: antinucleon
narrower: antiproton
narrower: positron

antiproton
type: Concept
broader: antiparticle
definition: antiproton
related: proton

antireflection coating
type: Concept
broader: coating
broader: optical film
broader: thin film
definition: antireflection coating
related: lens
related: optical surface

apastron
type: Concept
broader: apsis
definition: apastron
related: periastron

aperiodic comet
type: Concept
broader: comet
definition: aperiodic comet

aperture
type: Concept
definition: aperture
related: aperture synthesis
related: apodization
related: optical system

aperture synthesis
type: Concept
alternative label: synthetic aperture
definition: aperture synthesis
related: aperture
related: grading function
related: grating ring
related: interferometry
related: visibility function

apex
type: Concept
definition: apex
related: antapex
related: solar motion

aphelion
type: Concept
broader: apsis
definition: aphelion
related: Earth orbit
related: perihelion
related: planet

apocenter
type: Concept
definition: apocenter
related: binary star

apodization
type: Concept
alternative label: apodisation UK
definition: apodization
related: aperture
related: radio telescope

apogee
type: Concept
broader: apsis
definition: apogee
related: Moon
related: perigee

Apollo group
type: Concept
broader: minor planet family
definition: Apollo group
related: Amor group
related: Hirayama family
related: Trojan group

apparent intensity
type: Concept
broader: intensity
definition: apparent intensity

apparent magnitude
type: Concept
broader: magnitude
definition: apparent magnitude
narrower: B magnitude
narrower: H magnitude
narrower: I magnitude
narrower: J magnitude
narrower: K magnitude
narrower: L magnitude
narrower: M magnitude
narrower: N magnitude
narrower: O magnitude
narrower: P magnitude
narrower: Q magnitude
narrower: R magnitude
narrower: U magnitude
narrower: V magnitude
narrower: photoelectric magnitude
narrower: photographic magnitude
narrower: photovisual magnitude
related: photometric system
related: photometry

apparent position
type: Concept
alternative label: apparent places
broader: position
definition: apparent position
related: astrometry
related: true position

apparent superluminal motion
type: Concept
alternative label: superluminal motion
broader: motion
definition: apparent superluminal motion
related: velocity of light

apsidal motion
type: Concept
broader: motion
definition: apsidal motion
related: apsis
related: orbit

apsis
type: Concept
alternative label: apse
broader: orbital element
definition: apsis
narrower: apastron
narrower: aphelion
narrower: apogee
narrower: periastron
narrower: perigee
narrower: perihelion
related: apsidal motion
related: orbit
scope note: apse = apsis, apsides is plural

Ap star
type: Concept
alternative label: peculiar A star
broader: A star
broader: peculiar star
definition: Ap star
narrower: holmium star
narrower: manganese star
narrower: silicon star
narrower: spectrum variable star
related: alpha2 Canum Venaticorum star
related: magnetic star
related: magnetic variable star
related: oblique rotator
related: rapid oscillation

arc
type: Concept
change note: FVH: made general term (2007-OCT-1)
definition: arc
narrower: auroral arc
narrower: luminous arc

archaeoastronomy
type: Concept
alternative label: ancient astronomy
alternative label: astroarchaeology
broader: astronomy
broader: history of astronomy
definition: archaeoastronomy
narrower: megalithic astronomy
related: armillary sphere
related: astrolabe
related: astrology

argon
type: Concept
alternative label: Ar
broader: fundamental chemical element
definition: argon (atomic number 18)
history note: FVH: new (2007-OCT-25)

armillary sphere
type: Concept
broader: instrument
definition: armillary sphere
related: archaeoastronomy

array
type: Concept
definition: array
narrower: detector array
narrower: diode array
narrower: phased array
narrower: t array
narrower: telescope array
narrower: very long baseline interferometer
narrower: y array
related: antenna
related: grating response
related: interferometer
related: radio interferometer
related: radio telescope

array processor
type: Concept
broader: computer
definition: array processor
related: detector array

arsenic
type: Concept
alternative label: As
broader: fundamental chemical element
definition: arsenic (atomic number 33)
history note: FVH: new (2007-OCT-25)

artificial satellite
type: Concept
definition: artificial satellite
narrower: geostationary satellite
narrower: space observatory
related: polar orbit
related: satellite laser ranging
related: space astronomy
related: space telescope
related: space vehicle

ascending node
type: Concept
broader: node
change note: FVH: moved NODES to BT (2007-OCT-1)
definition: ascending node

ashen light
type: Concept
broader: atmospheric radiation
definition: ashen light
related: Venus
related: airglow
scope note: refers to Venus' atmosphere

A star
type: Concept
broader: early-type star
definition: A star
narrower: A dwarf
narrower: A giant
narrower: A subdwarf
narrower: A subgiant
narrower: A supergiant
narrower: Ae star
narrower: Am star
narrower: Ap star
related: early-type variable star
related: spectral type

astatine
type: Concept
alternative label: At
broader: fundamental chemical element
definition: astatine (atomic number 85)
history note: FVH: new (2007-OCT-25)

asteroid
type: Concept
alternative label: minor planet
alternative label: planetoid
broader: rotating body
definition: asteroid
narrower: near-Earth asteroid
related: Edgeworth-Kuiper belt
related: Kirkwood gap
related: Solar System
related: asteroid belt
related: asteroid occultation
related: interplanetary matter
related: meteor stream
related: meteorite
related: meteoroid
related: meteoroid dust cloud
related: minor planet family
related: planetesimal
related: resonance gap
related: trans-Neptunian object

asteroid belt
type: Concept
definition: asteroid belt
related: asteroid

asteroid occultation
type: Concept
broader: occultation
definition: occultation by asteroid
history note: FVH: new (2007-OCT-8)
related: asteroid

asteroseismology
type: Concept
alternative label: stellar seismology
broader: seismology
definition: asteroseismology
narrower: helioseismology
related: pulsating variable star
related: pulsation
related: rapid oscillation
related: solar oscillation
related: stellar oscillation

astigmatism
type: Concept
broader: optical aberration
definition: astigmatism
related: chromatic aberration
related: comatic aberration
related: distortion
related: field curvature
related: spherical aberration

astrobiology
type: Concept
alternative label: exobiology
broader: astronomy
broader: biology
broader: scientific field
definition: astrobiology
related: cosmochemistry
related: extraterrestrial life

astrodynamics
type: Concept
definition: astrodynamics
related: celestial mechanics

astrograph
type: Concept
broader: astrometric instrument
definition: astrograph

astrographic camera
type: Concept
broader: camera
definition: astrographic camera

astrographic catalog
type: Concept
alternative label: astrographic catalogues UK
broader: catalog
definition: astrographic catalog

astrolabe
type: Concept
broader: astrometric instrument
broader: instrument
definition: astrolabe
narrower: Danjon astrolabe
narrower: impersonal astrolabe
related: archaeoastronomy

astrology
type: Concept
broader: scientific field
definition: astrology
related: archaeoastronomy
related: astronomy
related: constellation
related: planet
related: zodiac

astrometric binary star
type: Concept
broader: binary star
definition: astrometric binary star

astrometric instrument
type: Concept
broader: instrument
definition: astrometric instrument
narrower: astrograph
narrower: astrolabe
narrower: quadrant
narrower: sextant
narrower: transit instrument
related: astrometry
related: time

astrometry
type: Concept
alternative label: positional astronomy
broader: astronomical technique
broader: astronomy
broader: observing technique
definition: astrometry
narrower: photographic astrometry
narrower: radio astrometry
narrower: space astrometry
related: Earth rotation
related: aberration
related: apparent position
related: astrometric instrument
related: astronomical geodesy
related: celestial mechanics
related: coordinate system
related: equator position
related: fundamental star
related: latitude determination
related: meridian circle
related: optical position
related: parallax
related: precession
related: reference system
related: stellar motion
related: transit
related: transit instrument
related: true position

astronomer
type: Concept
definition: astronomer
related: amateur astronomy
related: astronomical research

astronomical constant
type: Concept
broader: constant
definition: astronomical constant
narrower: Astronomical Unit
narrower: Oort constant
related: celestial mechanics
related: physical constant

astronomical geodesy
type: Concept
broader: geodesy
definition: astronomical geodesy
related: astrometry

astronomical optics
type: Concept
broader: optics
definition: astronomical optics

astronomical research
type: Concept
definition: astronomical research
narrower: space research
related: amateur astronomy
related: astronomer

astronomical technique
type: Concept
definition: astronomical technique
narrower: astrometry
narrower: interferometry
narrower: photometry
narrower: polarimetry
narrower: spectrophotometry
narrower: spectroscopy
related: analysis
related: observing technique
related: photography
related: reduction method
scope note: most used in several wavelength region

Astronomical Unit
type: Concept
alternative label: A.U.
alternative label: AU
broader: astronomical constant
change note: FVH: added ALT A.U. (2007-09-21)
definition: Astronomical Unit
related: annual parallax
related: distance scale
related: heliocentric correction
related: parallax
related: parsec
related: solar parallax
related: trigonometric parallax

astronomy
type: Concept
broader: scientific field
definition: astronomy
narrower: amateur astronomy
narrower: archaeoastronomy
narrower: astrobiology
narrower: astrometry
narrower: cosmic ray astronomy
narrower: cosmogony
narrower: cosmology
narrower: ground-based astronomy
narrower: infrared astronomy
narrower: space astronomy
related: astrology

astrophysics
type: Concept
broader: scientific field
change note: FVH: moved theoretical_astrophysics to NT (2007-OCT-1)
definition: astrophysics
narrower: high-energy astrophysics
narrower: theoretical astrophysics
related: cosmology
scope note: combine with other terms

A subdwarf
type: Concept
broader: A star
broader: subdwarf
definition: A subdwarf star
related: A dwarf

A subgiant
type: Concept
broader: A star
broader: subgiant
definition: A subgiant star

A supergiant
type: Concept
broader: A star
broader: early-type supergiant
broader: supergiant
definition: A supergiant star

asymptotic giant branch
type: Concept
alternative label: AGB
definition: asymptotic giant branch
related: Hertzsprung-Russell diagram
related: late-type giant
related: post-asymptotic giant branch

ataxite
type: Concept
broader: meteorite
definition: ataxite

atlas
type: Concept
alternative label: chart
definition: atlas
narrower: star atlas
related: catalog
related: finding chart
related: map
related: sky survey
related: survey

atmosphere
type: Concept
definition: atmosphere
narrower: Earth atmosphere
narrower: stellar atmosphere
related: aeronomy
related: air
related: boundary layer
related: greenhouse effect
related: limb brightening
related: limb darkening
related: macroturbulence
related: microturbulence
related: opacity
related: planet
related: radiation belt
related: refraction angle
related: scale height
related: scintillation
related: temperature zone
related: water vapor
scope note: combine with other terms

atmospheric density
type: Concept
broader: density
definition: atmospheric density
related: scale height

atmospheric extinction
type: Concept
alternative label: extinction
broader: absorption
broader: scattering
definition: atmospheric extinction
related: Earth atmosphere
related: absorption coefficient
related: atmospheric window
related: light absorption
related: light scattering
related: ultraviolet extinction
scope note: refers to Earth atmosphere

atmospheric radiation
type: Concept
alternative label: sky radiation
definition: atmospheric radiation
narrower: afterglow
narrower: airglow
narrower: ashen light
narrower: aurora
narrower: terrestrial radiation
related: sky brightness
scope note: ES: moved terrestrial_radiation from BT to NT (2007-OCT-8)

atmospheric refraction
type: Concept
definition: atmospheric refraction
related: active optics
related: adaptive optics
related: atmospheric scintillation
related: point spread function
related: refractive index
related: scintillation
related: seeing
related: speckle

atmospheric scattering
type: Concept
definition: atmospheric scattering
related: Earth atmosphere
related: absorption

atmospheric scintillation
type: Concept
alternative label: twinkling
broader: scintillation
definition: atmospheric scintillation
related: Earth atmosphere
related: atmospheric refraction
related: seeing

atmospheric tide
type: Concept
broader: tide
definition: atmospheric tide

atmospheric window
type: Concept
broader: window
definition: atmospheric window
narrower: infrared transmission window
narrower: optical transmission window
narrower: radio transmission window
related: Earth atmosphere
related: absorption
related: atmospheric extinction
related: transparency
scope note: spectral ranges transmitted by the Earth's atmosphere

atom
type: Concept
broader: matter
definition: atom
narrower: fundamental chemical element
related: chemical element

atomic clock
type: Concept
alternative label: caesium clock
alternative label: cesium clock
broader: clock
broader: measuring instrument
definition: atomic clock
related: atomic time
related: geodesy
related: time
related: time standard
related: time synchronization
related: very long baseline interferometry

atomic line
type: Concept
definition: atomic line
related: atomic spectrum

atomic physics
type: Concept
broader: scientific field
definition: atomic physics

atomic process
type: Concept
definition: atomic process
related: absorption line
related: emission line
related: equation of state
related: excitation
related: population inversion

atomic spectrum
type: Concept
broader: absorption spectrum
broader: spectrum
definition: atomic spectrum
related: atomic line

atomic time
type: Concept
definition: atomic time
related: atomic clock

attenuation
type: Concept
definition: attenuation
related: filter
related: neutral density filter

aurora
type: Concept
broader: atmospheric radiation
definition: aurora
narrower: auroral arc
narrower: auroral jet
related: Rayleigh
related: airglow
related: light emission
related: magnetic disturbances
related: magnetic pole
related: magnetic storm
related: night sky brightness
related: photoionization
related: sky brightness
related: solar activity
related: upper atmosphere

auroral arc
type: Concept
broader: arc
broader: aurora
definition: auroral arc

auroral jet
type: Concept
broader: aurora
definition: auroral jet

australite
type: Concept
broader: meteorite
broader: tektite
definition: australite
related: bediasite
related: chondrite
related: moldavite

auto-correlation
type: Concept
alternative label: autocorrelation
broader: correlation
definition: auto-correlation
history note: FVH: new (2007-NOV-1)
related: cross-correlation
related: data processing

autoguider
type: Concept
broader: control system
broader: guide system
definition: autoguider
related: automatic patrol telescope
related: quadrant detector
related: tracking

automated telescope
type: Concept
alternative label: robotic telescope
broader: telescope
definition: automated telescope
narrower: automatic patrol telescope
related: remote control system

automatic patrol telescope
type: Concept
broader: automated telescope
broader: optical telescope
definition: automatic patrol telescope
related: autoguider
related: photometry
related: remote control system

autumnal equinox
type: Concept
broader: equinox
definition: autumnal equinox
related: vernal equinox

auxiliary instrument
type: Concept
broader: instrument
definition: auxiliary instrument

avalanche photodiode
type: Concept
broader: photodiode
broader: photoelectronic device
definition: avalanche photodiode
related: photometry

axial ratio
type: Concept
broader: ratio
definition: axial ratio
history note: ES: new (2007-OCT-11)
related: axis
related: major axis
related: minor axis

axion
type: Concept
broader: elementary particle
definition: axion

axis
type: Concept
definition: axis
related: axial ratio
scope note: combine with other terms

azimuth
type: Concept
alternative label: bearing
definition: azimuth
related: altazimuth mounting
related: altitude angle
related: horizon
related: horizon coordinate system

Baade-Wesselink method
type: Concept
definition: Baade-Wesselink method
related: Cepheid
related: diameter

background
type: Concept
definition: background
scope note: combine with other terms

background noise
type: Concept
broader: noise
definition: background noise
related: cosmic noise
related: signal-to-noise ratio
related: sky noise

background radiation
type: Concept
alternative label: radiation background
broader: radiation
definition: background radiation
narrower: X-ray background
narrower: cosmic background radiation
narrower: cosmic ray
narrower: gamma-ray background
narrower: microwave background
narrower: radio background
narrower: ultraviolet background
related: Sunyaev-Zeldovich effect
related: anisotropy
related: cosmic noise
related: sky brightness

Bailey type
type: Concept
alternative label: AB variable star
broader: RR Lyrae star
definition: Bailey type

bailys bead
type: Concept
definition: Baily's bead
related: Sun
related: diamond ring effect
related: solar eclipse

Baker-Nunn camera
type: Concept
broader: catadioptric system
broader: meteor camera
broader: reflecting telescope
broader: wide-field telescope
definition: Baker-Nunn camera
related: Bouwers telescope
related: Schmidt telescope

balloon-borne instrument
type: Concept
alternative label: balloon borne instrument
definition: balloon-borne instrument
related: X-ray astronomy
related: airplane-borne instrument
related: cosmic ray astronomy
related: gamma-ray astronomy
related: ground-based astronomy
related: rocket-borne instrument
related: satellite-borne instrument
related: space probe instrument
related: space telescope
related: ultraviolet astronomy

Balmer continuum
type: Concept
broader: hydrogen spectrum
definition: Balmer continuum
related: Balmer series

Balmer limit
type: Concept
broader: Balmer series
definition: Balmer limit

Balmer series
type: Concept
alternative label: Balmer line
broader: hydrogen spectrum
definition: Balmer series
narrower: Balmer limit
narrower: H alpha
narrower: H beta
narrower: H delta
narrower: H epsilon
narrower: H gamma
related: Balmer continuum
related: Brackett series
related: Lyman series
related: Paschen series
related: Pfund series
related: absorption spectrum

barium
type: Concept
alternative label: Ba
broader: fundamental chemical element
definition: barium (atomic number 56)
history note: FVH: new (2007-OCT-25)
related: barium star

barium star
type: Concept
alternative label: Ba II star
broader: star
definition: barium star
narrower: semi-barium star
related: S star
related: barium
related: heavy metal star

barometer
type: Concept
broader: measuring instrument
definition: barometer
history note: FVH: new (2007-SEP-21)
related: pressure
related: weather station

barred spiral galaxy
type: Concept
broader: galaxy
broader: spiral galaxy
definition: barred spiral galaxy
narrower: B galaxy

baryon
type: Concept
broader: elementary particle
definition: baryon
related: Omega baryon
related: quark

baryonic Dark Matter
type: Concept
broader: Dark Matter
definition: baryonic Dark Matter
related: cold Dark Matter

basin
type: Concept
definition: basin
related: crater

B band
type: Concept
broader: Fraunhofer line
broader: molecular band
definition: B band
related: molecular spectrum

B dwarf
type: Concept
broader: B star
broader: dwarf
definition: B dwarf star
narrower: gamma Cassiopeiae star

beam switching
type: Concept
definition: beam switching
related: radio telescope

beam waveguide
type: Concept
definition: beam waveguide
related: collimator

beamwidth
type: Concept
definition: beamwidth
related: angular resolution
related: polar diagram
related: radio telescope

bediasite
type: Concept
broader: meteorite
broader: tektite
definition: bediasite
related: australite
related: chondrite
related: moldavite

berkelium
type: Concept
alternative label: Bk
broader: fundamental chemical element
definition: berkelium (atomic number 97)
history note: FVH: new (2007-OCT-25)

beryllium
type: Concept
alternative label: Be
broader: fundamental chemical element
definition: beryllium (atomic number 4)
history note: FVH: new (2007-OCT-25)

Besselian epoch
type: Concept
broader: epoch
broader: standard epoch
definition: Besselian epoch
related: Julian epoch
related: time

Bessel photometry
type: Concept
alternative label: Bessel UBVRI photometry
broader: broad band photometry
broader: photometric system
definition: Bessel photometry
history note: FVH: new (2007-SEP-21)
related: B magnitude
related: BV photometry
related: I magnitude
related: Johnson photometry
related: R magnitude
related: U magnitude
related: V magnitude

Be star
type: Concept
alternative label: Be dwarf star
broader: B star
broader: Herbig AeBe star
broader: early-type emission star
change note: FVH: moved Be_dwarf to ALT and U Herbig_star to BT HERBIG_AeBe_STARS (2007-OCT-1)
definition: Be star
narrower: Herbig AeBe star
narrower: lambda eridani star
related: Ae star
related: circumstellar shell

beta Cephei star
type: Concept
alternative label: beta Canis Majoris star
broader: early-type variable star
broader: multi-periodic variable star
broader: pulsating variable star
broader: short period variable star
definition: beta Cephei star
related: non-radial pulsation
related: radial pulsation

beta Lyrae star
type: Concept
broader: close binary star
broader: contact binary star
broader: eclipsing binary star
broader: ellipsoidal variable star
definition: beta Lyrae star

B galaxy
type: Concept
broader: barred spiral galaxy
definition: barred galaxy (Yerkes classification scheme)
history note: FVH+AG: new (2007-OCT-26)
related: Yerkes classification

B giant
type: Concept
broader: B star
broader: giant
definition: B giant star

Bianchi cosmology
type: Concept
broader: cosmology
definition: Bianchi cosmology

bias calibration
type: Concept
broader: calibration
definition: bias calibration
history note: FVH: new (2007-OCT-3)
related: CCD detector

Big Bang theory
type: Concept
broader: cosmology
definition: Big Bang theory
related: Friedmann universe
related: Hubble radius
related: Hubble time
related: Lemaitre universe
related: closed universe
related: early universe
related: hadron barrier
related: open universe
related: primordial fireball
related: relativistic velocity
related: steady-state theory

binary pulsar
type: Concept
broader: pulsar
definition: binary pulsar

binary star
type: Concept
alternative label: binaries
alternative label: double star
broader: binary system
broader: star
definition: binary star
narrower: Algol variable star
narrower: RS Canum Venaticorum star
narrower: astrometric binary star
narrower: close binary star
narrower: contact binary star
narrower: detached binary star
narrower: eclipsing binary star
narrower: ellipsoidal variable star
narrower: eruptive binary star
narrower: interacting binary star
narrower: semi-detached binary star
narrower: spectroscopic binary star
narrower: visual binary star
narrower: wide binary star
related: accretion
related: apocenter
related: center of mass
related: companion star
related: dynamical parallax
related: inclination
related: mass-loss
related: mass-ratio
related: multiple star
related: occultation
related: orbit
related: orbit determination
related: period
related: period change
related: period determination
related: phase wave
related: position angle
related: runaway star
related: semimajor axis
related: separation
related: two-body problem
related: von Zeipel theorem
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

binary system
type: Concept
definition: binary system
narrower: binary star
narrower: double galaxy

biology
type: Concept
broader: scientific field
definition: biology
narrower: astrobiology
narrower: space biology

bipolar galaxy
type: Concept
broader: galaxy
definition: bipolar galaxy

bipolar group
type: Concept
broader: sunspot group
definition: bipolar group
related: sunspot

bipolar nebula
type: Concept
broader: nebula
definition: bipolar nebula
related: bipolar outflow

bipolar outflow
type: Concept
alternative label: bipolar flow
broader: mass-loss
definition: bipolar outflow
related: bipolar nebula
related: circumstellar matter
related: radio source
related: radio structure

birth rate
type: Concept
definition: birth rate
related: mass function
related: protostar
related: star formation
related: stellar evolution

bismuth
type: Concept
alternative label: Bi
broader: fundamental chemical element
definition: bismuth (atomic number 83)
history note: FVH: new (2007-OCT-25)

black body radiation
type: Concept
alternative label: thermal black body radiation
broader: electromagnetic radiation
definition: black body radiation
related: brightness temperature
related: emissivity
related: thermal radiation
related: ultraviolet radiation

black dwarf
type: Concept
broader: dwarf
broader: low-mass star
broader: stellar object
definition: black dwarf star
related: white dwarf

black hole
type: Concept
broader: collapsed star
broader: compact object
broader: degenerate matter
broader: relativistic star
definition: black hole
narrower: Kerr black hole
narrower: stellar black hole
related: Hawking radiation
related: Kruskal diagram
related: Penrose process
related: Schwarzschild radius
related: X-ray binary star
related: accretion disk
related: ergosphere
related: event horizon
related: galactic nucleus
related: gravitational collapse
related: gravitational lensing
related: massive object
related: naked singularity
related: relativistic astrophysics
related: space-time singularity
related: supernova remnant
related: white hole

blank field
type: Concept
definition: blank field
related: galaxy void

blazar
type: Concept
broader: active galactic nucleus
definition: blazar
related: BL Lacertae object
related: quasar

Blazhko effect
type: Concept
definition: Blazhko effect
related: RR Lyrae star

BL Herculis star
type: Concept
broader: W Virginis star
broader: pulsating variable star
definition: BL Herculis star
related: Cepheid
related: RR Lyrae star
related: radial pulsation

blink comparator
type: Concept
broader: instrument
definition: blink comparator

blinking
type: Concept
definition: blinking
scope note: combine with other terms

BL Lacertae object
type: Concept
alternative label: BL Lac object
broader: compact object
broader: extragalactic radio source
broader: galaxy
broader: variable source
definition: BL Lacertae object
related: Seyfert galaxy
related: active galactic nucleus
related: blazar
related: compact galaxy
related: quasar

blue galaxy
type: Concept
broader: blue object
broader: galaxy
definition: blue galaxy

blue loop
type: Concept
broader: giant branch
definition: blue loop
history note: ES: new (2007-OCT-8)

blue object
type: Concept
definition: blue object
narrower: blue galaxy

blueshift
type: Concept
alternative label: blue shift
alternative label: blue-shift
broader: Doppler effect
broader: line shift
definition: blueshift
related: frequency shift

blue straggler star
type: Concept
broader: main sequence star
broader: young star
definition: blue straggler star
related: open star cluster

B magnitude
type: Concept
broader: apparent magnitude
definition: B magnitude
related: Bessel photometry
related: Johnson photometry

Bodes law
type: Concept
alternative label: Titius-Bode law
definition: Bode's law
related: Solar System
related: distance
related: planet

bohrium
type: Concept
alternative label: Bh
broader: fundamental chemical element
definition: bohrium (atomic number 107)
history note: FVH: new (2007-OCT-25)

Bok globule
type: Concept
broader: dark nebula
broader: globule
broader: interstellar matter
definition: Bok globule
related: H II region
related: cometary globule
related: protostar
related: star formation

bolide
type: Concept
broader: meteor
definition: bolide
related: fireball

bolometer
type: Concept
broader: instrument
definition: bolometer
related: bolometric correction
related: photometer
related: radiation
related: radiometer

bolometric correction
type: Concept
definition: bolometric correction
related: bolometer

boron
type: Concept
alternative label: B
broader: fundamental chemical element
definition: boron (atomic number 5)
history note: FVH: new (2007-OCT-25)

Bose-Einstein nucleus
type: Concept
broader: nucleus atom
definition: Bose-Einstein nucleus
related: Bose-Einstein statistics
related: Fermi-Dirac nucleus

Bose-Einstein statistics
type: Concept
definition: Bose-Einstein statistics
related: Bose-Einstein nucleus
related: Fermi-Dirac statistics
related: boson

boson
type: Concept
broader: elementary particle
broader: particle
definition: boson
narrower: alpha particle
narrower: composite particle
narrower: meson
narrower: photon
narrower: pion
related: Bose-Einstein statistics
related: fermion
related: hadron
related: lepton

boundary layer
type: Concept
definition: boundary layer
related: atmosphere
related: planet

bound-free transition
type: Concept
alternative label: bound free transition
definition: bound-free transition
related: absorption line
related: absorption spectrum

Bouwers telescope
type: Concept
broader: catadioptric system
broader: reflecting telescope
definition: Bouwers telescope
related: Baker-Nunn camera
related: Maksutov telescope
related: wide-field telescope

bow shock
type: Concept
broader: shock wave
definition: bow-shock

Bp star
type: Concept
broader: B star
broader: magnetic star
broader: peculiar star
definition: Bp star

Brackett series
type: Concept
broader: hydrogen spectrum
broader: infrared radiation
definition: Brackett series
related: Balmer series
related: Lyman series
related: Paschen series
related: Pfund series

bremsstrahlung
type: Concept
alternative label: free free transition
alternative label: free-free transition
broader: electromagnetic radiation
definition: bremsstrahlung
related: electron
related: radiation mechanism
related: spectrum
related: synchrotron radiation

bridge
type: Concept
definition: bridge
scope note: between galaxy

bright galaxy
type: Concept
broader: galaxy
definition: bright galaxy
related: Local Group
related: nearby galaxy

bright nebula
type: Concept
broader: nebula
definition: bright nebula

brightness
type: Concept
broader: optical property
definition: brightness
narrower: surface brightness
related: bright star
related: illumination
related: integration time
related: intensity
related: luminosity
related: magnitude

brightness distribution
type: Concept
definition: brightness distribution
scope note: see luminosity distribution

brightness temperature
type: Concept
broader: temperature
definition: brightness temperature
related: black body radiation
related: luminosity distribution
related: optical property

bright point
type: Concept
definition: solar bright point
history note: FVH: new (2007-OCT-29)
related: Sun

bright star
type: Concept
broader: high-luminosity star
broader: star
change note: FVH: correction from original IAU to reflect flux, not necessarily luminosity (2007-OCT-1)
definition: bright star
related: brightness

brillouin scattering
type: Concept
definition: Brillouin scattering
related: Mie scattering
related: brillouin spectrum

brillouin spectrum
type: Concept
broader: spectrum
definition: Brillouin spectrum
related: brillouin scattering
related: light scattering

broad band photometry
type: Concept
alternative label: wide-band photometry
broader: CCD photometry
broader: photoelectric photometry
broader: photographic photometry
change note: FVH: added BESSEL_PHOTOMETRY, GUNN_PHOTOMETRY, HST_PHOTOMETRY, KRON_COUSINS_PHOTOMETRY, SLOAN_PHOTOMETRY (2007-SEP-21)
definition: broad-band photometry
narrower: Bessel photometry
narrower: BV photometry
narrower: Cape photometry
narrower: Cape RI photometry
narrower: Gunn photometry
narrower: HST photometry
narrower: Johnson photometry
narrower: Kron-Cousins photometry
narrower: Sloan photometry
narrower: infrared photometry
narrower: rgb photometry
narrower: rgu photometry
narrower: two-color photometry
narrower: ultraviolet photometry
related: medium band photometry
related: narrow band photometry

bromine
type: Concept
alternative label: Br
broader: fundamental chemical element
definition: bromine (atomic number 35)
history note: FVH: new (2007-OCT-25)

brown dwarf
type: Concept
broader: late-type dwarf
broader: late-type subdwarf
broader: stellar object
definition: brown dwarf
narrower: L dwarf
narrower: L subdwarf
narrower: T dwarf
narrower: T subdwarf
related: dwarf
related: low-mass star
related: planetar

B star
type: Concept
broader: OB star
broader: early-type star
broader: young star
definition: B star
narrower: 53 Persei star
narrower: B dwarf
narrower: B giant
narrower: B subdwarf
narrower: B supergiant
narrower: Be star
narrower: Bp star
narrower: Bw star
narrower: mercury manganese star
related: O cluster
related: early-type variable star
related: spectral type

B subdwarf
type: Concept
broader: B star
broader: subdwarf
definition: B subdwarf star

B supergiant
type: Concept
broader: B star
broader: OB supergiant
broader: early-type supergiant
broader: supergiant
definition: B supergiant star

bubble
type: Concept
definition: bubble
narrower: interstellar bubble

bulge
type: Concept
definition: bulge
narrower: Galactic bulge
related: galaxy structure
scope note: combine with other terms

Burkert profile
type: Concept
broader: mass distribution
definition: Burkert mass-profile
history note: FVH: new (2007-OCT-5)
related: Navarro-Frenk-White profile
related: exponential profile
related: isothermal sphere

burst
type: Concept
definition: burst
narrower: X-ray burst
narrower: gamma-ray burst
narrower: optical burst
narrower: outburst
narrower: radio burst
narrower: rapid burst
related: burster
related: flare

burster
type: Concept
definition: burster
related: X-ray burst
related: burst
related: gamma-ray burst
related: optical burst
related: radio burst

butterfly diagram
type: Concept
definition: butterfly diagram
related: solar activity
related: solar cycle
related: sunspot
related: sunspot cycle
related: sunspot number

BV photometry
type: Concept
broader: broad band photometry
broader: two-color photometry
change note: FVH: added NT BESSEL_PHOTOMETRY, moved TWO-COLOR to BT and JOHNSON to NT (2007-SEP-21)
definition: BV photometry
related: Bessel photometry
related: Johnson photometry

Bw star
type: Concept
broader: B star
broader: helium-poor star
definition: Bw star

BY Draconis star
type: Concept
broader: flare star
definition: BY Draconis star
related: starspot

cadmium
type: Concept
alternative label: Cd
broader: fundamental chemical element
definition: cadmium (atomic number 48)
history note: FVH: new (2007-OCT-25)

caesium
type: Concept
alternative label: Cs
alternative label: cesium
broader: fundamental chemical element
definition: caesium (atomic number 55)
history note: FVH: new (2007-OCT-25)

Ca II emission line
type: Concept
broader: calcium line
broader: emission line
broader: metal line
definition: Ca II emission line
related: Wilson-Bappu effect

calcium
type: Concept
alternative label: Ca
broader: fundamental chemical element
definition: calcium (atomic number 20)
history note: FVH: new (2007-OCT-25)
related: calcium line

calcium line
type: Concept
broader: metal line
broader: spectral line
definition: calcium line
narrower: Ca II emission line
narrower: H and K line
narrower: K line
related: absorption line
related: calcium

calendar
type: Concept
definition: calendar
narrower: Gregorian calendar
narrower: Julian calendar
related: ephemeris
related: time

calibration
type: Concept
definition: calibration
narrower: bias calibration
narrower: dark-current calibration
narrower: dead-time calibration
narrower: linearity calibration
narrower: self-calibration method
related: comparison lamp
related: flat field lamp
related: instrument
related: lamp
related: measuring instrument
related: reseaux
scope note: combine with other terms

californium
type: Concept
alternative label: Cf
broader: fundamental chemical element
definition: californium (atomic number 98)
history note: FVH: new (2007-OCT-25)

camera
type: Concept
broader: optical instrument
broader: photographic instrument
definition: camera
narrower: Schmidt camera
narrower: all-sky camera
narrower: astrographic camera
narrower: ultraviolet camera
narrower: webcam
related: all-sky photography
related: camera lens
related: coronagraph
related: filter wheel
related: flat field lamp
related: photograph
related: photography
related: shutter
related: ultraviolet photography
related: wide-angle lens
scope note: photographic type only here

camera lens
type: Concept
broader: lens
definition: camera lens
related: camera

canyon
type: Concept
broader: surface of celestial body
definition: canyon
history note: FVH: new (2007-OCT-3)

Cape photometry
type: Concept
alternative label: UCBV photometry
broader: broad band photometry
broader: photometric system
definition: Cape photometry
related: Cape RI photometry
related: Johnson photometry
related: Kapteyn selected area

Cape RI photometry
type: Concept
broader: broad band photometry
definition: Cape RI photometry
related: Cape photometry
related: Johnson photometry

capture
type: Concept
definition: capture
related: absorption
scope note: combine with other terms

carbonaceous chondrite
type: Concept
broader: chondrite
definition: carbonaceous chondrite

carbon burning
type: Concept
broader: nuclear fusion
broader: nucleosynthesis
definition: carbon burning
related: carbon
related: carbon flash
related: giant
related: helium burning
related: hydrogen burning
related: nuclear reaction
related: oxygen burning
related: shell burning
related: silicon burning
related: stellar evolution
related: stellar interior

carbon
type: Concept
alternative label: C
broader: fundamental chemical element
definition: carbon (atomic number 6)
history note: FVH: new (2007-OCT-25)
related: carbon burning
related: carbon compound
related: carbon nitrogen cycle

carbon compound
type: Concept
broader: interstellar molecule
definition: carbon compound
narrower: CS
narrower: carbon dioxide
narrower: carbon disulfide
narrower: carbon monosulfide
narrower: carbon monoxide
narrower: cyanoacetylene
narrower: cyanodiacetylene
narrower: cyanogen
narrower: cyanopolyene
narrower: hydrated carbon
related: carbon

carbon dioxide
type: Concept
alternative label: CO2
alternative label: CO_2
broader: carbon compound
broader: gas
definition: carbon dioxide

carbon disulfide
type: Concept
broader: carbon compound
definition: carbon disulfide

carbon flash
type: Concept
alternative label: carbon detonation
definition: carbon flash
related: carbon burning
related: helium flash
related: nuclear fusion
related: red giant tip

carbon line
type: Concept
broader: metal line
broader: spectral line
definition: carbon line
narrower: C I emission

carbon monosulfide
type: Concept
alternative label: CS
broader: carbon compound
definition: carbon monosulfide

carbon monoxide
type: Concept
alternative label: CO
broader: carbon compound
broader: gas
definition: carbon monoxide
related: Swan band

carbon nitrogen cycle
type: Concept
alternative label: CNO cycle
alternative label: carbon cycle
broader: hydrogen burning
definition: carbon nitrogen cycle
related: CNO anomaly
related: carbon
related: nitrogen
related: nuclear fusion
related: proton-proton reaction
related: stellar interior

carbon star
type: Concept
alternative label: C star
broader: late-type giant
definition: carbon star
related: CH star
related: CN star
related: R star
related: S star
related: Wolf-Rayet star

Cassegrain antenna
type: Concept
alternative label: Cassegrain antennas
alternative label: two reflector antennas
alternative label: two-reflector antennas
broader: antenna
broader: radio telescope
definition: Cassegrain antenna
related: secondary mirror
related: subreflector

Cassegrain focus
type: Concept
broader: Cassegrain telescope
broader: focus
definition: Cassegrain focus
related: Coude focus
related: Nasmyth focus
related: Newtonian focus
related: parabolic antenna
related: prime focus
related: secondary mirror
related: subreflector

Cassegrain telescope
type: Concept
broader: telescope
definition: Cassegrain telescope
narrower: Cassegrain focus

cataclysmic variable star
type: Concept
alternative label: CV
alternative label: cataclysmic binary star
alternative label: eruptive variable star
broader: X-ray binary star
broader: close binary star
broader: eruptive binary star
broader: interacting binary star
broader: variable star
definition: cataclysmic variable star
narrower: AM Herculis star
narrower: SX Arietis star
narrower: UV Persei star
narrower: classical nova
narrower: dwarf nova
narrower: nova-like variable
related: eruption
related: low-mass X-ray binary star
related: mass exchange
related: mass-loss
related: optical outburst
related: supernova
related: symbiotic star
related: white dwarf

catadioptric system
type: Concept
broader: optical system
definition: catadioptric system
narrower: Baker-Nunn camera
narrower: Bouwers telescope
narrower: Maksutov telescope
narrower: Schmidt telescope
related: corrector plate
related: field corrector
related: lens
related: mirror
related: optical telescope

catalog
type: Concept
alternative label: catalogues UK
definition: catalog
narrower: Henry Draper catalog
narrower: astrographic catalog
narrower: radio source catalog
related: FK catalog system
related: atlas
related: ephemeris
related: finding list
related: fundamental star
related: map
related: nomenclature
related: sky survey
related: survey
related: ultraviolet survey
scope note: e.g. radio, star, x ray, etc.; combine with other terms

catastrophe theory
type: Concept
definition: catastrophe theory
related: mathematical analysis

cathode
type: Concept
broader: electrode
definition: cathode
narrower: photocathode
related: photomultiplier tube
related: quantum efficiency
related: thermionic emission

catoptric system
type: Concept
broader: optical system
definition: catoptric system
related: mirror
related: optical telescope

caustic
type: Concept
definition: caustic
history note: FVH: new (2007-OCT-8)
related: caustic crossing
related: cusp crossing
related: gravitational lensing

caustic crossing
type: Concept
definition: caustic crossing
history note: FVH: new (2007-OCT-8)
related: caustic
related: cusp
related: cusp crossing
related: gravitational lensing

CCD detector
type: Concept
alternative label: CCD camera
broader: multi-channel detector
broader: two-dimensional detector
definition: CCD detector
related: CCD observation
related: CCD photometry
related: bias calibration
related: charge-coupled device
related: dark-current calibration
related: photometer
related: television detector

CCD observation
type: Concept
broader: observation
definition: CCD observation
related: CCD detector
related: CCD photometry
related: charge-coupled device

CCD photometry
type: Concept
broader: photometry
definition: CCD photometry
narrower: broad band photometry
narrower: medium band photometry
narrower: narrow band photometry
related: CCD detector
related: CCD observation
related: charge-coupled device
related: photoelectric photometry
related: photographic photometry

cD galaxy
type: Concept
broader: D galaxy
broader: elliptical galaxy
broader: giant galaxy
broader: massive galaxy
definition: cD galaxy (compact D galaxy in the Yerkes classification scheme)
related: Yerkes classification
related: galaxy cluster
related: giant radio galaxy
related: nucleus celestial object

celestial coordinate system
type: Concept
broader: coordinate system
definition: celestial coordinate system
history note: FVH: new (2007-NOV-2)
narrower: Galactic coordinate system
narrower: ecliptic coordinate system
narrower: equatorial coordinate system
narrower: supergalactic coordinate system

celestial equator
type: Concept
broader: equatorial coordinate system
definition: celestial equator
related: Declination
related: Right Ascension
related: celestial pole
related: celestial sphere
related: equator correction
related: equator determination
related: equator position
related: equinox
related: obliquity of ecliptic

celestial mechanics
type: Concept
broader: scientific field
definition: celestial mechanics
related: Keplerian orbit
related: Lagrangian point
related: N-body problem
related: angular velocity
related: astrodynamics
related: astrometry
related: astronomical constant
related: gravitation
related: gravitational wave
related: lunar theory
related: orbit
related: orbital element
related: orbital evolution
related: orbital motion
related: orbital theory
related: osculatory element
related: perturbation
related: perturbation theory
related: planetary alignment
related: planetary theory
related: precession
related: three-body problem
related: two-body problem

celestial pole
type: Concept
broader: equatorial coordinate system
broader: pole
definition: celestial pole
narrower: North Celestial Pole
narrower: South Celestial Pole
related: celestial equator
related: celestial sphere
related: equator
related: polar axis

celestial sphere
type: Concept
definition: celestial sphere
related: celestial equator
related: celestial pole
related: horizon
related: meridian
related: zenith

celsius temperature scale
type: Concept
broader: temperature scale
definition: Celsius temperature scale
related: Kelvin
related: absolute temperature scale
related: temperature

center
type: Concept
definition: center
scope note: combine with other terms

center of mass
type: Concept
broader: orbital element
definition: center of mass
related: binary star
related: pericenter
related: planet

central star
type: Concept
broader: star
definition: central star
related: planetary nebula

centrifugal force
type: Concept
broader: force
definition: centrifugal force
related: centripetal force

centripetal force
type: Concept
broader: force
definition: centripetal force
related: centrifugal force

Cepheid
type: Concept
alternative label: Cepheid variable star
alternative label: bump Cepheid
alternative label: classical Cepheid
alternative label: delta Cephei star
broader: pulsating variable star
definition: Cepheid
narrower: double-mode Cepheid
narrower: young disk Cepheid
related: Baade-Wesselink method
related: BL Herculis star
related: Cepheid distance
related: He II ionization zone
related: RR Lyrae star
related: W Virginis star
related: dwarf Cepheid
related: instability strip
related: kappa mechanism
related: period-age relation
related: period-color relation
related: period-luminosity-color relation
related: period-luminosity relation
related: period-radius relation
related: period-spectrum relation
related: radial pulsation
related: radius-luminosity relation
scope note: most commonly used term

Cepheid distance
type: Concept
broader: distance measurement
definition: Cepheid distance
history note: ES: new (2007-OCT-8)
related: Cepheid

Cerenkov counter
type: Concept
alternative label: Cherenkov counter
broader: scintillation counter
definition: Cerenkov counter
related: Cerenkov radiation
related: cosmic ray
scope note: American spelling

Cerenkov radiation
type: Concept
alternative label: Cerenkov effect
broader: electromagnetic radiation
broader: radiation
definition: Cerenkov radiation
related: Cerenkov counter
related: cosmic ray
related: gamma-ray radiation
related: nuclear radiation
related: radiation mechanism
related: ultraviolet radiation
scope note: American spelling

Ceres
type: Concept
broader: dwarf planet
definition: Ceres
history note: FVH: new (2007-OCT-2)
related: Solar System

cerium
type: Concept
alternative label: Ce
broader: fundamental chemical element
broader: rare earth
definition: cerium (atomic number 58)
history note: FVH: new (2007-OCT-25)

Chandler wobble
type: Concept
alternative label: polar wandering
definition: Chandler wobble
related: Earth rotation
related: latitude determination
related: latitude variation
related: polar motion

Chandrasekhar mass
type: Concept
broader: mass
definition: Chandrasekhar limit
definition: Chandrasekhar limit; the mass-limit for a degenerate stellar object
related: gravitational collapse
related: hydrogen burning
related: mass-radius relation
related: stellar interior
related: white dwarf

Chandrasekhar-Schoenberg limit
type: Concept
alternative label: Chandrasekhar-Schonberg limit
alternative label: Schoenberg-Chandrasekhar limit
alternative label: Schonberg-Chandrasekhar limit
broader: mass
definition: Chandrasekhar-Schoenberg limit; the mass-limit for an isothermal stellar core
related: gravitational collapse
related: hydrogen burning
related: mass-radius relation
related: stellar interior

charge-coupled device
type: Concept
alternative label: CCD
alternative label: charge coupled device
broader: photoelectronic device
broader: semiconductor device
change note: FVH: added RT READ_OUT_NOISE (2007-SEP-21)
definition: charge-coupled device
related: CCD detector
related: CCD observation
related: CCD photometry
related: detector
related: multi-channel detector
related: quantum efficiency
related: read out noise
related: two-dimensional detector
scope note: use abbreviated form (CCD) when combined with other terms

charge-injection device
type: Concept
alternative label: CID
alternative label: charge injection device
broader: photoelectronic device
broader: semiconductor device
definition: charge-injection device
related: detector
related: two-dimensional detector

charge-transfer device
type: Concept
alternative label: CCD
alternative label: charge transfer device
broader: photoelectronic device
broader: semiconductor device
definition: charge-transfer device
related: detector
related: two-dimensional detector

chemical composition
type: Concept
definition: chemical composition
related: abundance
related: peculiar star

chemical element
type: Concept
definition: chemical element
narrower: fundamental chemical element
narrower: heavy element
narrower: isotope
narrower: trace element
related: abundance
related: atom
related: curve of growth
related: element formation
related: metal abundance
related: origin
scope note: see appendix

chemical evolution
type: Concept
definition: chemical evolution
narrower: enrichment
related: abundance
related: stellar evolution

chemiluminescence
type: Concept
broader: luminescence
definition: chemiluminescence
related: light emission

chemistry
type: Concept
broader: scientific field
definition: chemistry
narrower: cosmochemistry

chlorine
type: Concept
alternative label: Cl
broader: fundamental chemical element
definition: chlorine (atomic number 17)
history note: FVH: new (2007-OCT-25)

chondrite
type: Concept
broader: meteorite
definition: chondrite
narrower: achondrite
narrower: carbonaceous chondrite
narrower: chondrules
related: australite
related: bediasite
related: moldavite

chondrules
type: Concept
broader: chondrite
definition: chondrules

chromatic aberration
type: Concept
broader: optical aberration
definition: chromatic aberration
related: astigmatism
related: comatic aberration
related: distortion
related: field curvature
related: optical system
related: spherical aberration

chromium
type: Concept
alternative label: Cr
broader: fundamental chemical element
definition: chromium (atomic number 24)
history note: FVH: new (2007-OCT-25)

chromosphere
type: Concept
definition: chromosphere
related: Sun
related: coronal loop
related: facula
related: fibrill
related: flash spectrum
related: macro spicule
related: mottle
related: photosphere
related: plage
related: prominence
related: quiescent prominence
related: solar atmosphere
related: solar filament
related: spicule
related: stellar atmosphere
related: stellar wind
related: transition region

chronometer
type: Concept
alternative label: chronograph
broader: clock
broader: measuring instrument
definition: chronometer
related: time

CH star
type: Concept
broader: giant
definition: CH star
related: carbon star

C I emission
type: Concept
broader: carbon line
broader: emission spectrum
definition: C I emission

C II region
type: Concept
broader: interstellar matter
definition: C II region
related: dark cloud

circular orbit
type: Concept
broader: elliptical orbit
definition: circular orbit
related: hyperbolic orbit
related: orbital motion
related: parabolic orbit

circular polarization
type: Concept
alternative label: circular polarisation UK
broader: light polarization
change note: FVH: added RT QUARTER_WAVE_PLATES (2007-SEP-21)
definition: circular polarization
related: plane polarization
related: quarter wave plate

circumplanetary matter
type: Concept
broader: matter
definition: circumplanetary matter
related: circumstellar matter

circumstellar disk
type: Concept
broader: disk
broader: rotating body
definition: circumstellar discs UK
definition: circumstellar disk
related: accretion disk
related: circumstellar gas
related: circumstellar matter
related: mass-loss
related: torus

circumstellar dust
type: Concept
broader: circumstellar grain
broader: circumstellar matter
definition: circumstellar dust
related: R Coronae Borealis star
related: circumstellar gas
related: cocoon star
related: dust shell

circumstellar envelope
type: Concept
alternative label: stellar envelope
broader: circumstellar matter
definition: circumstellar envelope
narrower: expanding envelope
related: Wolf-Rayet star
related: circumstellar gas
related: circumstellar shell
related: mass-loss

circumstellar gas
type: Concept
broader: circumstellar matter
definition: circumstellar gas
related: circumstellar disk
related: circumstellar dust
related: circumstellar envelope
related: circumstellar grain
related: circumstellar shell

circumstellar grain
type: Concept
broader: circumstellar matter
definition: circumstellar grain
narrower: circumstellar dust
related: R Coronae Borealis star
related: circumstellar gas

circumstellar matter
type: Concept
alternative label: circumstellar cloud
alternative label: stellar envelope
broader: matter
definition: circumstellar matter
narrower: circumstellar dust
narrower: circumstellar envelope
narrower: circumstellar gas
narrower: circumstellar grain
related: bipolar outflow
related: circumplanetary matter
related: circumstellar disk
related: circumstellar shell
related: corona
related: expanding envelope
related: gravitating disk
related: interplanetary matter
related: interstellar matter
related: mass-loss

circumstellar shell
type: Concept
alternative label: stellar envelope
broader: shell
definition: circumstellar shell
narrower: dust shell
narrower: rotating shell
related: Be star
related: circumstellar envelope
related: circumstellar gas
related: circumstellar matter
related: extreme carbon star
related: mass-loss
related: shell star
related: stellar wind

civil time
type: Concept
broader: time
definition: civil time
related: Universal Time
related: ephemeris time
related: mean solar time
related: sidereal time

classical nova
type: Concept
alternative label: nova
broader: cataclysmic variable star
broader: nova
definition: classical nova
history note: FVH: new (2007-NOV-15)

classical T Tauri star
type: Concept
alternative label: CTTS
broader: T Tauri star
definition: classical T Tauri star
history note: FVH: new (2007-SEP-24)

classification
type: Concept
definition: classification
narrower: luminosity classification
narrower: spectral classification
related: morphology
related: nomenclature
related: taxonomy
scope note: combine with other terms

clean method
type: Concept
definition: clean method
related: data processing
related: image processing
related: image reconstruction
related: radio astronomy

clock
type: Concept
broader: measuring instrument
broader: timing equipment
definition: clock
narrower: atomic clock
narrower: chronometer
related: time
related: time standard

close binary star
type: Concept
broader: binary star
definition: close binary star
narrower: Z Andromedae star
narrower: beta Lyrae star
narrower: cataclysmic variable star
narrower: ellipsoidal variable star
narrower: semi-detached binary star
related: Roche limit
related: Roche lobe
related: X-ray bright point
related: accretion disk
related: contact binary star
related: synchronous rotation
related: tidal friction

closed universe
type: Concept
broader: cosmology
definition: closed universe
related: Big Bang theory
related: open universe
related: steady-state theory

close encounter
type: Concept
definition: close encounter
related: stellar dynamics

cloud
type: Concept
definition: cloud
narrower: collapsing cloud
narrower: dust cloud
narrower: gas cloud
narrower: high-velocity cloud
narrower: noctilucent cloud
narrower: plasma cloud
related: Earth atmosphere
related: cloud monitor
scope note: combine with other terms

cloud monitor
type: Concept
broader: all-sky camera
definition: cloud monitor
history note: FVH: new (2007-SEP-21)
related: Earth atmosphere
related: cloud

clumping
type: Concept
definition: clumping
scope note: combine with other terms

cluster
type: Concept
definition: cluster
narrower: galaxy cluster
narrower: protocluster
narrower: star cluster

clustering
type: Concept
definition: clustering
related: galaxy cluster
related: star cluster
scope note: combine with other terms

CNO anomaly
type: Concept
broader: anomaly
definition: CNO anomaly
related: abundance
related: abundance ratio
related: carbon nitrogen cycle
related: metal abundance

CN star
type: Concept
broader: giant
definition: cn star
related: carbon star
scope note: carbon-nitrogen star

coating
type: Concept
definition: coating
narrower: aluminum coating
narrower: antireflection coating
narrower: silver coating
related: lens
related: mirror
related: thin film
related: vapor deposition
scope note: combine with other terms

cobalt
type: Concept
alternative label: Co
broader: fundamental chemical element
definition: cobalt (atomic number 27)
history note: FVH: new (2007-OCT-25)
related: magnetic star

cocoon star
type: Concept
broader: infrared source
definition: cocoon star
related: circumstellar dust

coelostat
type: Concept
broader: reflecting telescope
definition: coelostat
narrower: heliostat
related: drive
related: siderostat
related: telescope mounting

coherence
type: Concept
definition: coherence
narrower: light coherence
related: laser
related: maser
scope note: combine with other terms

cold Dark Matter
type: Concept
broader: Dark Matter
change note: FVH: added RT DARK_ENERGY (2007-SEP-21)
definition: cold Dark Matter
related: Dark Energy
related: baryonic Dark Matter
related: cosmology

collapse
type: Concept
definition: collapse
narrower: gravitational collapse
scope note: combine with other terms

collapsed star
type: Concept
alternative label: collapsed object
alternative label: collapsing star
broader: star
definition: collapsed star
narrower: black hole
narrower: neutron star
narrower: pulsar
narrower: stellar black hole
related: degenerate star
related: stellar evolution
related: white dwarf

collapsing cloud
type: Concept
broader: cloud
definition: collapsing cloud
narrower: protoplanetary nebula
related: protocluster
related: protogalaxy
related: protostar

collimation
type: Concept
definition: collimation
related: adjustment
related: alignment optics
related: correction
related: optics
related: orientation

collimator
type: Concept
definition: collimator
related: beam waveguide
related: lens
related: mirror
related: optical instrument

collisional excitation
type: Concept
broader: collision process
definition: collisional excitation
related: collision broadening
related: collision spectroscopy
related: collision strength
related: ion
related: ionized gas
related: spectroscopy

collisional plasma
type: Concept
broader: plasma
definition: collisional plasma
related: collision process
related: ion
related: shock

collision broadening
type: Concept
broader: collision process
broader: line broadening
definition: collision broadening
related: collision spectroscopy
related: collision strength
related: collisional excitation
related: spectroscopic analysis

collision
type: Concept
definition: collision
related: galaxy
related: meteorite
related: planet
scope note: combine with other terms

collision process
type: Concept
definition: collision process
narrower: collision broadening
narrower: collisional excitation
related: collision strength
related: collisional plasma

collision spectroscopy
type: Concept
broader: spectroscopy
definition: collision spectroscopy
related: collision broadening
related: collision strength
related: collisional excitation

collision strength
type: Concept
definition: collision strength
related: collision broadening
related: collision process
related: collision spectroscopy
related: collisional excitation

color
type: Concept
broader: optical property
definition: color
related: color equation
related: color excess
related: color-luminosity relation
related: color-magnitude relation
related: color photography
related: color-redshift relation
related: colorimetry
related: electromagnetic radiation
related: photometry
related: spectrophotometry
related: temperature
related: visible radiation

color equation
type: Concept
definition: color equation
related: color
related: photometry

color excess
type: Concept
definition: color excess
related: color
related: interstellar reddening
related: photometry

colorimetry
type: Concept
definition: colorimetry
related: color

color index
type: Concept
definition: color index
related: intrinsic color
related: photometry
related: two-color diagram

color-luminosity relation
type: Concept
alternative label: color luminosity relation
definition: color-luminosity relation
related: Hertzsprung-Russell diagram
related: color
related: photometry

color-magnitude relation
type: Concept
alternative label: c m diagram
alternative label: c m relation
alternative label: c-m diagram
alternative label: c-m relation
alternative label: color magnitude relation
alternative label: color-magnitude diagram
definition: color-magnitude relation
related: Hertzsprung-Russell diagram
related: color
related: photometry

color photography
type: Concept
broader: photography
definition: color photography
related: color

color-redshift relation
type: Concept
alternative label: color redshift relation
definition: color-redshift relation
related: color
related: cosmology
related: observational cosmology

color vision
type: Concept
broader: vision
definition: color vision
related: dark adaption

coma
type: Concept
definition: coma
related: comet
related: galaxy

comatic aberration
type: Concept
alternative label: coma
broader: optical aberration
change note: FVH: renamed after general conversion to singular (2007-11-27)
definition: comatic aberration (coma)
related: astigmatism
related: chromatic aberration
related: distortion
related: field curvature
related: optical system
related: spherical aberration

cometary globule
type: Concept
broader: dark nebula
broader: globule
broader: interstellar matter
definition: cometary globule
history note: FVH: new (2007-SEP-21)
related: Bok globule
related: H II region
related: protostar
related: star formation

comet
type: Concept
broader: rotating body
definition: comet
narrower: Kreutz sungrazer
narrower: aperiodic comet
narrower: long period comet
narrower: periodic comet
related: Oort cloud
related: Solar System
related: coma
related: dirty snowball theory
related: dust
related: envelope
related: halo
related: interplanetary matter
related: jet
related: meteor stream
related: meteorite
related: meteoroid
related: meteoroid dust cloud
related: nucleus celestial object
related: parabolic orbit
related: streamer
related: tail
scope note: named comet not included

compact galaxy
type: Concept
broader: peculiar galaxy
definition: compact galaxy
narrower: N galaxy
related: BL Lacertae object
related: active galaxy
related: quasar

compact H II region
type: Concept
broader: H II region
definition: compact H II region

compact nebula
type: Concept
broader: nebula
definition: compact nebula

compact nucleus
type: Concept
broader: galactic nucleus
broader: nucleus celestial object
definition: compact nucleus
narrower: Seyfert nucleus
related: Seyfert galaxy
related: active galactic nucleus
related: compact source

compact object
type: Concept
definition: compact object
narrower: BL Lacertae object
narrower: black hole
narrower: compact source
narrower: neutron star
narrower: white dwarf

compact source
type: Concept
broader: compact object
broader: radio source
broader: source
definition: compact source
related: compact nucleus
related: radio structure

companion galaxy
type: Concept
broader: galaxy
definition: companion galaxy
related: double galaxy
related: galaxy group

companion star
type: Concept
broader: star
definition: companion star
narrower: primary star
narrower: secondary star
narrower: tertiary star
related: binary star
related: multiple star

comparison
type: Concept
definition: comparison
scope note: combine with other terms

comparison lamp
type: Concept
broader: lamp
definition: comparison lamp
history note: FVH: new (2007-SEP-21)
related: calibration
related: spectrograph

comparison star
type: Concept
broader: standard star
definition: comparison star
related: variable star

component
type: Concept
definition: component
scope note: combine with other terms

composite particle
type: Concept
broader: boson
definition: composite particle
narrower: alpha particle
narrower: ion
narrower: radical

composition
type: Concept
definition: composition
related: planet
scope note: combine with other terms

Compton effect
type: Concept
definition: Compton effect
related: X-ray scattering
related: electron
related: radiation scattering

Compton scattering
type: Concept
broader: light scattering
broader: radiation scattering
broader: scattering
definition: Compton scattering
narrower: Thomson scattering
related: Rayleigh scattering
related: electron
related: inverse Compton scattering

computer application
type: Concept
broader: computing
definition: computer application
narrower: computer simulation

computer
type: Concept
definition: computer
narrower: array processor
narrower: microprocessor
narrower: parallel computer
related: computing
related: control system
related: data center
related: data processing
related: data reduction
related: data storage
related: peripheral

computer model
type: Concept
broader: computing
broader: model
definition: computer model
related: computer program
related: computer simulation
related: mathematical model
related: numerical simulation

computer program
type: Concept
broader: computing
definition: computer program
related: computer model
related: computer simulation
related: data processing

computer simulation
type: Concept
broader: computer application
broader: simulation
definition: computer simulation
related: computer model
related: computer program

computing
type: Concept
definition: computing
narrower: computer application
narrower: computer model
narrower: computer program
narrower: data processing
narrower: data retrieval
narrower: data storage
narrower: database
related: computer

condensation
type: Concept
definition: condensation
scope note: combine with other terms

conduction
type: Concept
definition: conduction
related: energy-transfer
related: thermal conductivity
scope note: combine with other terms

conjunction
type: Concept
definition: conjunction
related: opposition
related: quadrature
related: synodic period
related: syzygy
scope note: refers to planet position

constant
type: Concept
change note: FVH: more physical hierarchy (2007-OCT-11)
definition: constant
narrower: astronomical constant
narrower: cosmological parameter
narrower: physical constant

constellation
type: Concept
definition: constellation
related: astrology
related: zodiac
scope note: see appendix

contact binary star
type: Concept
broader: binary star
definition: contact binary star
narrower: beta Lyrae star
narrower: ellipsoidal variable star
related: close binary star
related: eclipsing binary star
related: equipotential surface
related: mass exchange

continental drift
type: Concept
definition: continental drift
related: continent
related: geomagnetism
related: geophysics
related: paleomagnetism

continent
type: Concept
definition: continent
related: Earth
related: continental drift

continuous spectrum
type: Concept
broader: spectrum
definition: continuous spectrum
related: light emission
related: spectroscopic analysis
related: spectroscopy
related: visible spectrum

continuum radiation
type: Concept
broader: electromagnetic radiation
broader: radiation
definition: continuum radiation
narrower: X-ray continuum
narrower: ultraviolet continuum
related: contiuum
related: photosphere

contiuum
type: Concept
definition: contiuum
related: continuum radiation
related: spectrum
scope note: combine with other terms

contour map
type: Concept
broader: map
definition: contour map
related: isophot
related: radio structure

contraction
type: Concept
definition: contraction
scope note: combine with other terms

contrast
type: Concept
definition: contrast
scope note: combine with other terms

control system
type: Concept
definition: control system
narrower: autoguider
narrower: remote control system
related: computer
related: drive
related: guide system
related: microprocessor
related: pointing accuracy
related: pointing error
related: quadrant detector
related: telescope
related: telescope instrument
related: tracking

convection
type: Concept
definition: convection
related: Hayashi track
related: Rayleigh number
related: convective envelope
related: convective shell
related: convective zone
related: dredge up
related: energy-transfer
related: envelope
related: granulation
related: line broadening
related: mass-transfer
related: thermal instability
related: thermal structure
related: turbulence Earth atmosphere
related: turbulence star atmosphere

convective envelope
type: Concept
definition: convective envelope
related: convection

convective shell
type: Concept
broader: shell
definition: convective shell
related: convection

convective zone
type: Concept
definition: convective zone
related: convection

cooling
type: Concept
definition: cooling
scope note: combine with other terms

cooling flow
type: Concept
definition: cooling flow
related: accretion disk
related: galaxy
related: star formation

coordinated Universal Time
type: Concept
alternative label: UTC
broader: Universal Time
definition: coordinated Universal Time
history note: FVH: new (2007-OCT-3)
related: UT1

coordinate system
type: Concept
definition: coordinate system
narrower: celestial coordinate system
narrower: horizon coordinate system
narrower: inertial coordinate system
related: aberration
related: astrometry
related: heliocentric correction
related: position
related: reference frame
related: reference system
related: spherical coordinate
related: true position
scope note: coordinate not included
scope note: planet and satellite surface

copper
type: Concept
alternative label: Cu
broader: fundamental chemical element
definition: copper (atomic number 29)
history note: FVH: new (2007-OCT-25)

core
type: Concept
definition: core
related: Earth
related: planet
related: stellar interior
scope note: combine with other terms

corona
type: Concept
alternative label: coronas
definition: corona
narrower: E corona
narrower: F corona
narrower: K corona
narrower: coronal hole
narrower: coronal line
narrower: coronal loop
narrower: coronal plume
narrower: solar corona
related: circumstellar matter
related: halo
related: ionization
related: mass-loss
related: stellar atmosphere

coronagraph
type: Concept
broader: instrument
broader: optical instrument
definition: coronagraph
related: camera
related: solar corona
related: solar observatory
related: spectroheliograph

coronal dimming
type: Concept
definition: solar coronal dimming
history note: FVH: new (2007-OCT-29)
related: solar corona

coronal hole
type: Concept
broader: corona
definition: coronal hole
related: solar corona
related: solar wind

coronal line
type: Concept
broader: corona
broader: emission line
definition: coronal line
related: solar corona

coronal loop
type: Concept
broader: corona
definition: coronal loop
related: chromosphere
related: solar activity
related: solar corona

coronal mass ejection
type: Concept
alternative label: CME
broader: mass-loss
definition: coronal mass ejection
related: corpuscular emission
related: solar corona

coronal plume
type: Concept
broader: corona
definition: coronal plume
related: solar corona

coronal transient
type: Concept
definition: coronal transient
related: solar corona

coronal wave
type: Concept
broader: Alfven wave
definition: solar coronal wave
history note: FVH: new (2007-OCT-29)
related: solar corona

corpuscular emission
type: Concept
definition: corpuscular emission
related: coronal mass ejection

correction
type: Concept
definition: correction
related: adjustment
related: alignment optics
related: collimation
related: error
related: selection effect
scope note: combine with other terms

corrector plate
type: Concept
broader: lens
broader: optical component
definition: corrector plate
related: Schmidt camera
related: Schmidt telescope
related: catadioptric system
related: field corrector

correlation
type: Concept
definition: correlation
history note: FVH: new (2007-NOV-1)
narrower: auto-correlation
narrower: cross-correlation
narrower: interferometric correlation
narrower: luminosity-dispersion relation
related: interferometry
related: receiver

cosmic abundance
type: Concept
broader: abundance
definition: cosmic abundance
related: cosmology

cosmic background radiation
type: Concept
broader: background radiation
definition: cosmic background radiation

cosmic
type: Concept
definition: cosmic
scope note: combine with other terms

cosmic electrodynamics
type: Concept
broader: electrodynamics
broader: electromagnetic theory
definition: cosmic electrodynamics
related: magnetohydrodynamics

cosmic noise
type: Concept
broader: noise
broader: radio interference
definition: cosmic noise
narrower: microwave background
related: background noise
related: background radiation
related: microwave emission
related: radio background

cosmic ray astronomy
type: Concept
broader: astronomy
definition: cosmic ray astronomy
related: balloon-borne instrument
related: high-energy astrophysics
related: rocket-borne instrument
related: satellite-borne instrument

cosmic ray
type: Concept
alternative label: cosmic radiation
alternative label: primary cosmic ray
broader: background radiation
broader: high-energy radiation
broader: radiation
definition: cosmic ray
narrower: Galactic cosmic ray
related: Cerenkov counter
related: Cerenkov radiation
related: cosmic ray shower
related: cosmic ray source
related: forbush effect
related: inverse Compton effect
related: secondary cosmic ray

cosmic ray shower
type: Concept
alternative label: air shower
alternative label: auger shower
definition: cosmic ray shower
related: cosmic ray
related: phosphorescent scintillation
related: secondary cosmic ray

cosmic ray source
type: Concept
broader: source
definition: cosmic ray source
related: cosmic ray

cosmic string
type: Concept
alternative label: string
definition: cosmic string
related: cosmology
related: intergalactic matter
related: interstellar matter
related: large scale structure

cosmic year
type: Concept
broader: year
definition: cosmic year
related: Galactic rotation

cosmochemistry
type: Concept
alternative label: astrochemistry
alternative label: cosmic chemistry
broader: chemistry
definition: cosmochemistry
related: astrobiology
related: cosmology
related: interstellar molecule
related: molecular astrophysics

cosmochronology
type: Concept
alternative label: nucleocosmochronology
definition: cosmochronology
history note: ES: new (2007-OCT-8)
related: age
related: cosmology
related: nuclear fission

cosmogony
type: Concept
broader: astronomy
definition: cosmogony
narrower: relativity
related: cosmology
related: protocluster
related: protogalaxy
related: protoplanetary nebula
related: universe

cosmological constant
type: Concept
alternative label: Lambda
broader: cosmological parameter
change note: FVH: added ALT lambda (2007-SEP-21)
definition: cosmological constant
related: Dark Energy
related: Omega Lambda
related: cosmology

cosmological distance scale
type: Concept
broader: distance scale
definition: cosmological distance scale
related: Hubble constant
related: cosmological parameter
related: deceleration parameter
related: observational cosmology
related: redshift
related: redshift distance relation
related: redshift magnitude relation

cosmological model
type: Concept
definition: cosmological model
scope note: see under cosmology

cosmological parameter
type: Concept
broader: constant
change note: FVH: renamed *_parameter, since some of them aren't necessarily constant (2007-OCT-26)
definition: cosmological parameter/constant
history note: FVH: new (2007-SEP-21)
narrower: Hubble constant
narrower: Omega parameter
narrower: cosmological constant
narrower: deceleration parameter
narrower: sigma8
related: cosmological distance scale
related: cosmology

cosmology
type: Concept
broader: astronomy
change note: FVH: added RT DARK_ENERGY, RT LARGE_SCALE_STRUCTURE (2007-SEP-21)
definition: cosmology
narrower: Bianchi cosmology
narrower: Big Bang theory
narrower: Einstein universe
narrower: Friedmann universe
narrower: Goedel universe
narrower: Lemaitre universe
narrower: closed universe
narrower: de Sitter universe
narrower: dirac cosmology
narrower: expanding universe
narrower: hierarchical cosmology
narrower: inflationary universe
narrower: open universe
narrower: oscillating universe
narrower: primordial fireball
narrower: quantum cosmology
narrower: relativistic cosmology
narrower: steady-state theory
related: Dark Energy
related: Dark Matter
related: Hubble constant
related: Hubble diagram
related: Hubble law
related: Hubble radius
related: Hubble time
related: Omega parameter
related: Tully-Fisher relation
related: Type Ia supernova
related: anthropic principle
related: astrophysics
related: cold Dark Matter
related: color-redshift relation
related: cosmic abundance
related: cosmic string
related: cosmochemistry
related: cosmochronology
related: cosmogony
related: cosmological constant
related: cosmological parameter
related: early universe
related: galaxy count
related: galaxy distribution
related: galaxy evolution
related: general theory of relativity
related: large scale structure
related: microwave background
related: missing mass
related: protocluster
related: protogalaxy
related: redshift
related: redshift distance relation
related: redshift magnitude relation
related: relativistic astrophysics
related: relativistic velocity
related: space-time curvature
related: stellar evolution
related: universe
related: white hole

Coude focus
type: Concept
broader: focus
definition: Coude focus
related: Cassegrain focus
related: Nasmyth focus
related: Newtonian focus
related: prime focus

Coude spectrograph
type: Concept
broader: spectrograph
definition: Coude spectrograph
related: high-resolution spectrosopy
related: high-resolution spectrum

Coude spectrum
type: Concept
broader: high-resolution spectrum
definition: Coude spectrum
related: echelle spectrograph

counter
type: Concept
alternative label: count
broader: measuring instrument
definition: counter
narrower: scintillation counter
related: counting
related: data acquisition
related: photon counting system

counting
type: Concept
alternative label: count
definition: counting
related: counter
related: data acquisition

coupling
type: Concept
definition: coupling
scope note: combine with other terms

crater
type: Concept
definition: crater
narrower: impact crater
related: Earth
related: Moon
related: basin
related: ejecta
related: meteor
related: planet
related: volcano
scope note: combine with other terms

cross-correlation
type: Concept
alternative label: cross correlation
broader: correlation
definition: cross-correlation
related: auto-correlation
related: data processing
related: interferometric correlation

crustal dynamics
type: Concept
definition: crustal dynamics
related: Moon
related: crust
related: mantle

crust
type: Concept
definition: crust
related: Earth
related: Moon
related: crustal dynamics
related: mantle
related: planet
scope note: combine with other terms

cryogenics
type: Concept
definition: cryogenics
related: cryostat
related: outgassing
related: temperature control

cryostat
type: Concept
definition: cryostat
related: cryogenics
related: temperature control

CS
type: Concept
broader: carbon compound
broader: hydrocarbon
broader: interstellar molecule
definition: CS molecule
history note: FVH: new (2007-OCT-2)

curium
type: Concept
alternative label: Cm
broader: fundamental chemical element
definition: curium (atomic number 96)
history note: FVH: new (2007-OCT-25)

current
type: Concept
definition: current
related: antenna
related: current sheet
related: electric current
scope note: combine with other terms

current sheet
type: Concept
definition: current sheet
related: antenna
related: current
related: electric current

curve of growth
type: Concept
definition: curve of growth
related: abundance
related: chemical element

cusp crossing
type: Concept
definition: cusp crossing
history note: FVH: new (2007-OCT-8)
related: caustic
related: caustic crossing
related: cusp
related: gravitational lensing

cusp
type: Concept
definition: cusp
history note: FVH: new (2007-OCT-8)
related: caustic crossing
related: cusp crossing
related: gravitational lensing

cyanoacetylene
type: Concept
broader: carbon compound
definition: cyanoacetylene

cyanodiacetylene
type: Concept
broader: carbon compound
definition: cyanodiacetylene

cyanogen
type: Concept
alternative label: CN
broader: carbon compound
definition: cyanogen

cyanogen line
type: Concept
broader: spectral line
definition: cyanogen line
related: absorption line

cyanopolyene
type: Concept
broader: carbon compound
change note: FVH: corrected spelling (2007-OCT-2)
definition: cyanopolyene

cycle
type: Concept
definition: cycle
related: period

cyclotron radiation
type: Concept
broader: electromagnetic radiation
broader: radiation
broader: synchrotron radiation
definition: cyclotron radiation
related: radiation mechanism

damping constant
type: Concept
definition: damping constant
related: line formation
related: radiation damping
related: radiative braking

Danjon astrolabe
type: Concept
broader: astrolabe
definition: Danjon astrolabe

dark adaption
type: Concept
alternative label: retinal adaption
definition: dark adaption
related: color vision
related: darkness
related: night vision
related: vision

dark cloud
type: Concept
broader: interstellar matter
definition: dark cloud
related: C II region

dark-current calibration
type: Concept
broader: calibration
definition: dark-current calibration
history note: FVH: new (2007-OCT-3)
related: CCD detector

Dark Energy
type: Concept
alternative label: dark energy
definition: Dark Energy
history note: FVH: new (2007-SEP-21)
related: Dark Matter
related: Hubble law
related: cold Dark Matter
related: cosmological constant
related: cosmology
related: early universe
related: galaxy count
related: galaxy distribution
related: general theory of relativity
related: redshift distance relation
related: redshift magnitude relation
related: space-time curvature
related: universe

Dark Matter
type: Concept
broader: intergalactic matter
broader: interstellar matter
definition: Dark Matter
narrower: baryonic Dark Matter
narrower: cold Dark Matter
related: Dark Energy
related: Galactic rotation
related: cosmology
related: elementary particle
related: galaxy rotation curve
related: mass distribution

dark nebula
type: Concept
alternative label: absorption nebula
broader: interstellar matter
broader: nebula
definition: dark nebula
narrower: Bok globule
narrower: cometary globule
related: Wolf diagram
related: globule
related: star formation

darkness
type: Concept
definition: darkness
related: dark adaption
related: diurnal variation
related: electromagnetic radiation
related: optical property
related: visible radiation

darkroom
type: Concept
definition: darkroom
related: photographic processing
related: photography

darmtadtium
type: Concept
alternative label: Ds
broader: fundamental chemical element
definition: darmtadtium (atomic number 110)
history note: FVH: new (2007-OCT-25)

DA star
type: Concept
broader: white dwarf
change note: FVH: modified from original DA_star (2007-OCT-1)
definition: DA white dwarf star
related: DB star
related: DO star

data acquisition
type: Concept
definition: data acquisition
related: counter
related: counting
related: data analysis
related: digital recorder
related: observation
related: observing technique

data analysis
type: Concept
broader: analysis
definition: data analysis
narrower: error analysis
related: data acquisition
related: data processing
related: data reduction
related: data storage
related: determination

database
type: Concept
alternative label: data base
broader: computing
definition: database
related: data center
related: data retrieval
related: data storage
related: virtual observatory

data center
type: Concept
definition: data center
related: computer
related: data processing
related: data reduction
related: data retrieval
related: data storage
related: database
related: on-line system
related: virtual observatory

data processing
type: Concept
broader: computing
definition: data processing
narrower: Monte Carlo technique
narrower: data reduction
narrower: numerical analysis
related: auto-correlation
related: clean method
related: computer
related: computer program
related: cross-correlation
related: data analysis
related: data center
related: data retrieval
related: data storage
related: error analysis
related: observing technique
related: on-line system
related: reduction method

data reduction
type: Concept
broader: data processing
definition: data reduction
related: computer
related: data analysis
related: data center
related: data retrieval
related: data storage
related: error analysis
related: fine analysis
related: reduction method

data retrieval
type: Concept
broader: computing
definition: data retrieval
related: data center
related: data processing
related: data reduction
related: data storage
related: database
related: virtual observatory

data storage
type: Concept
broader: computing
definition: data storage
narrower: RAID array
narrower: analog recorder
related: computer
related: data analysis
related: data center
related: data processing
related: data reduction
related: data retrieval
related: database

DB star
type: Concept
broader: helium-rich star
broader: white dwarf
definition: DB white dwarf star
history note: FVH: new (2007-OCT-1)
related: DA star
related: DO star

DDO photometry
type: Concept
broader: medium band photometry
broader: photometric system
definition: DDO photometry

dead-time calibration
type: Concept
broader: calibration
definition: dead-time calibration
history note: FVH: new (2007-OCT-3)

decay oscillation
type: Concept
definition: decay of oscillation
related: amplitude
related: oscillation
related: radiation damping

deceleration
type: Concept
definition: deceleration
related: acceleration
related: deceleration parameter

deceleration parameter
type: Concept
alternative label: q-parameter
broader: cosmological parameter
definition: deceleration parameter
related: cosmological distance scale
related: deceleration

Declination
type: Concept
alternative label: celestial latitude
broader: equatorial coordinate system
broader: latitude
definition: Declination
related: Right Ascension
related: celestial equator
related: equator
related: equatorial zone

deconvolution
type: Concept
definition: deconvolution
scope note: combine with other terms

defect
type: Concept
definition: defect
scope note: combine with other terms

deformation
type: Concept
definition: deformation
scope note: combine with other terms

degenerate dwarf
type: Concept
broader: degenerate star
definition: degenerate dwarf star
narrower: white dwarf

degenerate matter
type: Concept
broader: matter
definition: degenerate matter
narrower: black hole
narrower: degenerate star

degenerate star
type: Concept
broader: degenerate matter
broader: subluminous star
definition: degenerate star
narrower: degenerate dwarf
narrower: neutron star
narrower: pulsar
related: collapsed star
related: mass-radius relation

delta delphini star
type: Concept
broader: delta Scuti star
broader: pulsating variable star
definition: delta Delphini star

delta Scuti star
type: Concept
alternative label: AI Velorum star
broader: multi-periodic variable star
broader: pulsating variable star
broader: short period variable star
definition: delta Scuti star
narrower: delta delphini star
related: He II ionization zone
related: dwarf Cepheid
related: kappa mechanism
related: non-radial pulsation
related: radial pulsation

dense cloud
type: Concept
broader: interstellar matter
broader: nebula
definition: dense cloud

densitometer
type: Concept
broader: measuring instrument
definition: densitometer
related: densitometry
related: microdensitometer

densitometry
type: Concept
definition: densitometry
related: densitometer

density bounded
type: Concept
definition: density bounded
related: density

density
type: Concept
alternative label: specific gravity
definition: density
narrower: atmospheric density
narrower: electron density
narrower: energy density
narrower: gas density
narrower: mass density
related: Rankine-Hugoniot relation
related: density bounded
related: density distribution
related: density fluctuation
related: density perturbation
related: density variation
related: density wave model

density distribution
type: Concept
definition: density distribution
related: density

density fluctuation
type: Concept
definition: density fluctuation
related: density

density perturbation
type: Concept
definition: density perturbation
related: density

density variation
type: Concept
definition: density variation
related: density

density wave model
type: Concept
definition: density wave model
related: density

descending node
type: Concept
broader: node
change note: FVH: moved NODES to BT (2007-OCT-1)
definition: descending node

design
type: Concept
definition: design
narrower: engineering
related: research
scope note: combine with other terms

de Sitter universe
type: Concept
broader: cosmology
definition: de Sitter universe

destruction
type: Concept
definition: destruction
scope note: combine with other terms

detached binary star
type: Concept
broader: binary star
definition: detached binary star
narrower: W Ursae Majoris star
related: semi-detached binary star

detection
type: Concept
definition: detection
narrower: signal detection
scope note: combine with other terms

detector array
type: Concept
broader: array
definition: detector array
related: array processor

detector
type: Concept
broader: instrument
change note: FVH: added NT SUPERCONDUCTING_TUNNEL_JUNCTION (2007-SEP-21)
definition: detector
narrower: X-ray detector
narrower: dust detector
narrower: infrared detector
narrower: multi-channel detector
narrower: photographic emulsion
narrower: photomultiplier tube
narrower: radiometer
narrower: superconducting tunnel junction
narrower: synchronous detector
narrower: two-dimensional detector
narrower: ultraviolet detector
related: charge-coupled device
related: charge-injection device
related: charge-transfer device
related: limiting magnitude
related: pixel
related: quantum efficiency
related: receiver
related: remote sensing
related: semiconductor device
related: sensitivity
related: shot noise
related: shutter
related: signal detection
related: telescope instrument
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

determination
type: Concept
definition: determination
related: data analysis
related: measurement
related: quantization

deuterium
type: Concept
broader: hydrogen
definition: deuterium, an isotope of hydrogen
related: isotope

D galaxy
type: Concept
broader: elliptical galaxy
broader: galaxy
definition: rotationally symmetric elliptical galaxy (Yerkes classification scheme)
narrower: cD galaxy
related: Yerkes classification
related: massive galaxy

diagram
type: Concept
definition: diagram
scope note: combine with other terms

diameter
type: Concept
broader: dimension
definition: diameter
narrower: angular diameter
narrower: isophotal diameter
related: Baade-Wesselink method
related: occultation
related: surface gravity
scope note: combine with other terms

diamond ring effect
type: Concept
definition: diamond ring effect
related: Sun
related: bailys bead
related: solar eclipse

dichroic mirror
type: Concept
broader: mirror
definition: dichroic mirror
related: optical film
related: optical filter

Dicke radiometer
type: Concept
broader: radiometer
definition: Dicke radiometer

differential equation
type: Concept
broader: mathematical analysis
definition: differential equation

differential image motion monitor
type: Concept
alternative label: DIMM
broader: seeing monitor
definition: differential image-motion monitor
history note: FVH: new (2007-SEP-21)

differential rotation
type: Concept
broader: rotation
change note: FVH: added RT Galactic_rotation, RT galaxy_rotation_curve (2007-OCT-5)
definition: differential rotation
related: Galactic rotation
related: galaxy
related: galaxy rotation curve
related: globular star cluster
related: tidal disruption
related: tidal distortion

diffraction
type: Concept
definition: diffraction
narrower: X-ray diffraction
related: Airy disk
related: Rayleigh criterion
related: diffraction patterns
related: interference wave
related: shadow band

diffraction grating
type: Concept
alternative label: grating
broader: optical component
definition: diffraction grating
narrower: VPH grating
narrower: echelle grating
narrower: objective grating
narrower: reflection grating
narrower: transmission grating
related: grating spectrograph
related: grism
related: spectrograph
related: spectrum

diffraction patterns
type: Concept
definition: diffraction patterns
related: diffraction

diffuse nebula
type: Concept
broader: nebula
definition: diffuse nebula

diffuse radiation
type: Concept
definition: diffuse radiation
scope note: combine with other terms

diffusion
type: Concept
definition: diffusion
scope note: combine with other terms

digital image
type: Concept
broader: image
definition: digital image

digital recorder
type: Concept
definition: digital recorder
related: data acquisition

dimension
type: Concept
definition: dimension
narrower: diameter
scope note: combine with other terms

diode array
type: Concept
broader: array
broader: multi-channel detector
definition: diode array
related: reticon array

diode
type: Concept
broader: electronic equipment
definition: diode

dioptric system
type: Concept
broader: optical system
definition: dioptric system
related: lens
related: optical telescope

dipole antenna
type: Concept
alternative label: dipole antennas
broader: antenna
broader: directional antenna
definition: dipole antenna
related: dipole

dipole
type: Concept
definition: dipole
narrower: half-wave dipole
related: dipole antenna
related: electric charge
related: electric dipole

dirac cosmology
type: Concept
broader: cosmology
definition: Dirac cosmology

directional antenna
type: Concept
alternative label: directional antennas
broader: antenna
definition: directional antenna
narrower: Mills cross antenna
narrower: Yagi antenna
narrower: dipole antenna
narrower: parabolic antenna

dirty snowball theory
type: Concept
definition: dirty snowball theory
related: comet
related: nucleus celestial object

discoloration
type: Concept
definition: discoloration
scope note: combine with other terms

discoveries
type: Concept
definition: discoveries
related: research
related: space exploration
scope note: combine with other terms

discrete radio source
type: Concept
broader: radio source
definition: discrete radio source

dish antenna
type: Concept
alternative label: dish antennas
broader: radio telescope
definition: dish antenna
related: antenna
related: parabolic reflector
related: radar telescope

disintegration
type: Concept
definition: disintegration
scope note: combine with other terms

disk
type: Concept
definition: discs UK
definition: disk
narrower: accretion disk
narrower: circumstellar disk
narrower: gaseous disk
narrower: gravitating disk
related: disk flaring
related: disk galaxy
related: disk population
related: disk star

disk flaring
type: Concept
definition: disc flaring UK
definition: disk flaring
related: disk
related: morphology

disk galaxy
type: Concept
broader: galaxy
definition: disc galaxy UK
definition: disk galaxy
narrower: lenticular galaxy
narrower: spiral galaxy
related: disk
related: mass distribution

disk population
type: Concept
broader: population II star
definition: disc population UK
definition: disk population
related: Galactic plane
related: disk
related: stellar population

disk star
type: Concept
broader: population II star
definition: disc star UK
definition: disk star
related: Galactic plane
related: disk
related: gaseous disk

dispersion
type: Concept
definition: dispersion
scope note: combine with other terms

disruption
type: Concept
definition: disruption
scope note: combine with other terms

dissipation
type: Concept
definition: dissipation
scope note: combine with other terms

distance
type: Concept
definition: distance
related: Bodes law
related: absolute magnitude
related: distance indicator
related: distance measurement
related: distance modulus
related: distance scale
related: light year
related: parallax
related: parsec
related: range finder
related: trigonometric parallax

distance indicator
type: Concept
definition: distance indicator
related: distance
related: distance measurement
related: distance modulus
related: distance scale

distance measurement
type: Concept
definition: distance measurement
narrower: Cepheid distance
narrower: Faber-Jackson distance
narrower: RGB tip distance
narrower: SBF distance
related: distance
related: distance indicator
related: distance scale

distance modulus
type: Concept
alternative label: modulus
definition: distance modulus
related: absolute magnitude
related: distance
related: distance indicator
related: distance scale
related: parallax

distance scale
type: Concept
definition: distance scale
narrower: cosmological distance scale
related: Astronomical Unit
related: distance
related: distance indicator
related: distance measurement
related: distance modulus
related: parsec

distortion
type: Concept
broader: optical aberration
definition: distortion
related: astigmatism
related: chromatic aberration
related: comatic aberration
related: field curvature
related: optical system
related: spherical aberration

distribution function
type: Concept
broader: function
definition: distribution function
related: distribution in space
related: frequency distribution
related: statistics
scope note: in mathematics

distribution in space
type: Concept
definition: distribution in space
related: distribution function
scope note: combine with other terms

diurnal parallax
type: Concept
broader: parallax
definition: diurnal parallax
narrower: horizontal parallax
related: zenith distance

diurnal phenomena
type: Concept
definition: diurnal phenomena
related: diurnal variation

diurnal variation
type: Concept
definition: diurnal variation
related: darkness
related: diurnal phenomena

D layer
type: Concept
alternative label: D region
definition: D layer
related: Earth atmosphere
related: ionosphere

D line
type: Concept
broader: spectral line
definition: D line
related: absorption spectrum

dome
type: Concept
alternative label: telescope dome
definition: dome
related: dome seeing
related: observatory
related: telescope
related: temperature control
related: ventilation
scope note: excluding lunar dome

dome seeing
type: Concept
broader: seeing
definition: dome seeing
related: dome
related: ventilation

Doppler broadening
type: Concept
broader: line broadening
definition: Doppler broadening
related: Doppler effect
related: Stark broadening
related: Zeeman splitting
related: line width
related: natural line width
related: pressure broadening

Doppler effect
type: Concept
definition: Doppler effect
narrower: blueshift
narrower: redshift
related: Doppler broadening
related: line shift
related: radar
related: radial velocity
related: spectroscopic analysis
related: spectroscopic binary star
related: stellar motion

DO star
type: Concept
broader: white dwarf
definition: DO white dwarf star
history note: FVH: new (2007-OCT-9)
narrower: PG1159 star
related: DA star
related: DB star

double galaxy
type: Concept
alternative label: binary galaxy
broader: binary system
broader: galaxy
definition: double galaxy
related: companion galaxy
related: galaxy merger

double-mode Cepheid
type: Concept
alternative label: beat_Cepheid
alternative label: double mode Cepheid
broader: Cepheid
broader: double-mode variable star
broader: pulsating variable star
definition: double-mode Cepheid
related: double-mode pulsation

double-mode pulsation
type: Concept
alternative label: double mode pulsation
broader: multi-periodic pulsation
definition: double-mode pulsation
related: double-mode Cepheid
related: double-mode variable star
related: pulsating variable star

double-mode variable star
type: Concept
alternative label: double mode variable star
broader: multi-periodic variable star
broader: pulsating variable star
definition: double-mode variable star
narrower: RR Lyrae star
narrower: double-mode Cepheid
related: double-mode pulsation

double quasar
type: Concept
broader: gravitationally lensed source
definition: double quasar
related: gravitational deflection
related: gravitational lensing
related: quasar

DQ Herculis star
type: Concept
broader: eclipsing binary star
broader: slow nova
definition: DQ Herculis star

dredge up
type: Concept
definition: dredge up
related: convection
related: giant
related: metal abundance
related: stellar atmosphere
related: stellar interior

drift scan
type: Concept
definition: drift scan
related: photometry
related: radio structure
related: surface photometry

drift wave
type: Concept
broader: wave
definition: drift wave

drive
type: Concept
definition: drive
related: coelostat
related: control system
related: siderostat
related: telescope

dubnium
type: Concept
alternative label: Db
broader: fundamental chemical element
definition: dubnium (atomic number 105)
history note: FVH: new (2007-OCT-25)

dust cloud
type: Concept
broader: cloud
broader: interstellar matter
definition: dust cloud
related: dust
related: interstellar dust

dust detector
type: Concept
broader: detector
definition: dust detector
related: dust

dust
type: Concept
alternative label: cosmic dust
broader: intergalactic matter
broader: interstellar matter
definition: dust
narrower: interplanetary dust
narrower: interstellar dust
narrower: zodiacal dust
related: comet
related: dust cloud
related: dust detector
related: dust grain
related: dust nebula
related: dust shell
related: dust storm
related: gas to dust ratio

dust grain
type: Concept
broader: interstellar matter
definition: dust grain
related: adsorption
related: dust

dust nebula
type: Concept
broader: interstellar matter
broader: nebula
definition: dust nebula
related: dust

dust shell
type: Concept
broader: circumstellar shell
broader: shell
definition: dust shell
related: circumstellar dust
related: dust
related: symbiotic star

dust storm
type: Concept
definition: dust storm
related: dust
related: planet
related: surface of celestial body

dwarf Cepheid
type: Concept
broader: irregular variable star
broader: multi-periodic variable star
broader: pulsating variable star
definition: dwarf Cepheid
related: Cepheid
related: delta Scuti star

dwarf
type: Concept
broader: main sequence star
definition: dwarf star
narrower: A dwarf
narrower: B dwarf
narrower: F dwarf
narrower: G dwarf
narrower: K dwarf
narrower: M dwarf
narrower: O dwarf
narrower: black dwarf
narrower: flare star
narrower: late-type dwarf
narrower: nearby dwarf
related: brown dwarf
related: low-luminosity star
related: low-mass star
related: luminosity classification
related: main sequence
related: subdwarf
scope note: the term alone refers to main sequence star, but subterms may refer to evolved star

dwarf galaxy
type: Concept
broader: galaxy
broader: peculiar galaxy
definition: dwarf galaxy

dwarf nova
type: Concept
alternative label: DN
broader: cataclysmic variable star
broader: eruptive binary star
change note: FVH: total update (2007-SEP-24)
definition: dwarf nova
narrower: SU Ursae Majoris star
narrower: SX Arietis star
narrower: U Geminorum star
narrower: WZ Sagittae star
narrower: Z Camelopardalis star
related: AM Canum Venaticorum star
related: UV Persei star
related: UX Ursae Majoris star
related: X-ray binary star
related: accretion disk
related: emission line star

dwarf planet
type: Concept
broader: rotating body
definition: dwarf planet
narrower: Ceres
narrower: Pluto
related: planet

dynamical evolution
type: Concept
broader: evolution
definition: dynamical evolution

dynamical friction
type: Concept
broader: friction
definition: dynamical friction
related: radiative braking

dynamical parallax
type: Concept
broader: parallax
definition: dynamical parallax
related: binary star
related: kinematic parallax
related: moving cluster parallax

dynamical time
type: Concept
broader: time
definition: dynamical time

dynamics
type: Concept
definition: dynamics
scope note: combine with other terms

dynamo theory
type: Concept
definition: dynamo theory
related: magnetic field

dysprosium
type: Concept
alternative label: Dy
broader: fundamental chemical element
broader: rare earth
definition: dysprosium (atomic number 66)
history note: FVH: new (2007-OCT-25)

early-type emission star
type: Concept
alternative label: early type emission star
broader: emission line star
definition: early-type emission star
narrower: Ae star
narrower: Be star
narrower: Oe star
narrower: Oef star
narrower: Of star
narrower: Wolf-Rayet star

early-type galaxy
type: Concept
alternative label: early type galaxy
broader: galaxy
definition: early-type galaxy

early-type star
type: Concept
alternative label: blue star
alternative label: early type star
alternative label: hot star
broader: ultraviolet source
definition: early-type star
narrower: A star
narrower: B star
narrower: O star
narrower: OB star
narrower: early-type variable star
narrower: faint blue star
related: orion population star
scope note: see also gas

early-type supergiant
type: Concept
alternative label: early type supergiant star
broader: supergiant
definition: early-type supergiant star
narrower: A supergiant
narrower: B supergiant
narrower: O supergiant
narrower: OB supergiant
related: luminous blue variable star

early-type variable star
type: Concept
alternative label: early type variable star
broader: early-type star
definition: early-type variable star
narrower: S Doradus star
narrower: SX Arietis star
narrower: beta Cephei star
narrower: luminous blue variable star
related: A star
related: B star
related: O star

early universe
type: Concept
definition: early universe
related: Big Bang theory
related: Dark Energy
related: cosmology

Earth
type: Concept
broader: planet
definition: Earth
related: Earth sciences
related: Solar System
related: continent
related: core
related: crater
related: crust
related: earthquake
related: geocorona
related: geodesy
related: geoid
related: geomagnetism
related: geophysics
related: glaciology
related: mantle
related: perigee
related: polar cap
related: radiation belt
related: scintillation
related: seismology
related: sidereal time
related: solar-terrestrial relation
related: space geodesy
related: topography
related: troposphere
scope note: combine with other terms

Earth atmosphere
type: Concept
alternative label: terrestrial atmosphere
broader: atmosphere
definition: Earth atmosphere
related: D layer
related: E layer
related: F layer
related: aeronomy
related: atmospheric extinction
related: atmospheric scattering
related: atmospheric scintillation
related: atmospheric window
related: cloud
related: cloud monitor
related: exosphere
related: ionosphere
related: magnetosphere
related: mesopause
related: mesosphere
related: meteorology
related: noctilucent cloud
related: ozone layer
related: scale height
related: scintillation
related: seeing
related: stratopause
related: stratosphere
related: telluric line
related: thermosphere
related: tropopause
related: troposphere
related: turbulence Earth atmosphere
related: twilight
related: upper atmosphere

Earth-Moon system
type: Concept
alternative label: Earth Moon system
definition: Earth-Moon system
related: Solar System
related: annual equation
related: equation of the center
related: lunar theory
related: tidal friction
related: two-body problem

Earth orbit
type: Concept
definition: Earth orbit
related: annual equation
related: aphelion
related: ecliptic
related: ecliptic coordinate system
related: ecliptic plane
related: equation of time
related: perihelion
related: solar parallax
related: time
related: tropical year
related: zodiac

earthquake
type: Concept
definition: earthquake
related: Earth
related: moonquake

Earth rotation
type: Concept
broader: rotation
definition: Earth rotation
related: Chandler wobble
related: astrometry
related: equation of the equinox
related: nutation
related: polar motion
related: precession
related: time

Earth sciences
type: Concept
broader: scientific field
definition: Earth sciences
narrower: geodesy
narrower: geology
narrower: geophysics
narrower: glaciology
related: Earth
related: geophysical observatory

Earthshine
type: Concept
definition: Earthshine
related: Moon

eccentric anomaly
type: Concept
broader: orbital anomaly
definition: eccentric anomaly

eccentricity
type: Concept
broader: orbital element
definition: eccentricity
related: elliptical orbit

echelle grating
type: Concept
alternative label: echelons
broader: diffraction grating
definition: echelle grating
related: echelle spectrum
related: objective grating
related: reflection grating
related: spectrograph
related: transmission grating

echelle spectrograph
type: Concept
alternative label: echelle spectrometer
broader: spectrograph
definition: echelle spectrograph
related: Coude spectrum
related: echelle spectrum
related: high-resolution spectrosopy
related: high-resolution spectrum

echelle spectrum
type: Concept
broader: high-resolution spectrum
broader: spectrum
definition: echelle spectrum
related: echelle grating
related: echelle spectrograph

eclipse
type: Concept
definition: eclipse
narrower: annular eclipse
narrower: lunar eclipse
narrower: partial eclipse
narrower: solar eclipse
narrower: total eclipse
related: eclipsing binary star
related: occultation
related: penumbra
related: transit
related: umbra

eclipsing binary star
type: Concept
alternative label: eclipsing star
alternative label: eclipsing variable star
alternative label: photometric binary star
broader: binary star
broader: variable star
definition: eclipsing binary star
narrower: Algol variable star
narrower: DQ Herculis star
narrower: R Canis Majoris star
narrower: W Ursae Majoris star
narrower: beta Lyrae star
narrower: upsilon Sagittarii star
related: Roche lobe
related: contact binary star
related: eclipse
related: ellipsoidal variable star
related: interacting binary star
related: partial eclipse
related: photometric element
related: spectroscopic binary star
related: total eclipse

ecliptic coordinate system
type: Concept
broader: celestial coordinate system
definition: ecliptic coordinate system
related: Earth orbit
related: ecliptic
related: ecliptic latitude
related: ecliptic longitude
related: ecliptic pole

ecliptic
type: Concept
definition: ecliptic
related: Earth orbit
related: ecliptic coordinate system
related: ecliptic plane
related: ecliptic pole
related: equinox
related: obliquity of ecliptic
related: solstice
related: zodiac

ecliptic latitude
type: Concept
broader: latitude
definition: ecliptic latitude
related: ecliptic coordinate system
related: ecliptic longitude
related: ecliptic pole

ecliptic longitude
type: Concept
broader: longitude
definition: ecliptic longitude
related: ecliptic coordinate system
related: ecliptic latitude
related: ecliptic pole

ecliptic plane
type: Concept
definition: ecliptic plane
related: Earth orbit
related: ecliptic
related: ecliptic pole
related: obliquity of ecliptic

ecliptic pole
type: Concept
broader: pole
definition: ecliptic pole
narrower: North Ecliptic Pole
narrower: South Ecliptic Pole
related: ecliptic
related: ecliptic coordinate system
related: ecliptic latitude
related: ecliptic longitude
related: ecliptic plane

E corona
type: Concept
alternative label: E component
alternative label: E-corona
broader: corona
definition: E corona

Eddington limit
type: Concept
definition: Eddington limit
related: gravitational force
related: radiation pressure
related: stellar interior

edge effect
type: Concept
definition: edge effect
related: galaxy
related: photography

Edgeworth-Kuiper belt
type: Concept
alternative label: Kuiper belt
definition: Edgeworth-Kuiper belt
history note: FVH: new (2007-OCT-2)
related: Edgeworth-Kuiper belt object
related: Solar System
related: asteroid
related: trans-Neptunian object

Edgeworth-Kuiper belt object
type: Concept
alternative label: EKO
alternative label: KBO
alternative label: Kuiper belt object
broader: trans-Neptunian object
definition: Edgeworth-Kuiper belt object
related: Edgeworth-Kuiper belt

effective temperature
type: Concept
broader: temperature
definition: effective temperature
related: electromagnetic radiation
related: photometry
related: radiation
related: standard candle

e-folding time
type: Concept
definition: e-folding time
related: oscillation

E galaxy
type: Concept
broader: elliptical galaxy
definition: elliptical galaxy (Yerkes classification scheme)
history note: FVH: new (2007-OCT-12)
narrower: Ep galaxy
related: Yerkes classification

Einstein coefficient
type: Concept
definition: Einstein coefficient
related: absorption coefficient
related: emission coefficient

Einstein effect
type: Concept
alternative label: Einstein shift
definition: Einstein effect
related: gravitational redshift

einsteinium
type: Concept
alternative label: Es
broader: fundamental chemical element
definition: einsteinium (atomic number 99)
history note: FVH: new (2007-OCT-25)

Einstein ring
type: Concept
broader: gravitationally lensed source
definition: Einstein ring
related: gravitational deflection
related: gravitational lensing

Einstein universe
type: Concept
broader: cosmology
definition: Einstein universe

ejecta
type: Concept
definition: ejecta
related: Wolf-Rayet star
related: crater

ejection
type: Concept
definition: ejection
scope note: combine with other terms

elasticity
type: Concept
definition: elasticity
scope note: combine with other terms

E layer
type: Concept
alternative label: E region
definition: E layer
related: Earth atmosphere
related: ionosphere
scope note: refers to Earth atmosphere

electrical property
type: Concept
definition: electrical property
related: electricity

electric charge
type: Concept
definition: electric charge
related: dipole
related: electricity
related: electrostatic wave

electric current
type: Concept
definition: electric current
related: current
related: current sheet
related: electricity

electric dipole
type: Concept
definition: electric dipole
related: dipole
related: electricity

electric field
type: Concept
definition: electric field
related: Paul trap
related: electricity
related: electrostatic wave
related: force

electricity
type: Concept
definition: electricity
related: electric charge
related: electric current
related: electric dipole
related: electric field
related: electrical property

electrode
type: Concept
definition: electrode
narrower: cathode
narrower: photocathode
related: image tube
related: photomultiplier tube

electrodynamics
type: Concept
definition: electrodynamics
narrower: cosmic electrodynamics

electromagnetic
type: Concept
definition: electromagnetic
scope note: combine with other terms

electromagnetic field
type: Concept
definition: electromagnetic field
related: electromagnetic forces
related: field equation
related: quantum field theory
related: radiation field

electromagnetic forces
type: Concept
broader: force
definition: electromagnetic forces
related: electromagnetic field

electromagnetic interaction
type: Concept
broader: interaction
definition: electromagnetic interaction

electromagnetic radiation
type: Concept
alternative label: electromagnetic wave
broader: radiation
broader: wave
change note: FVH+ES: moved radiation to BT, lots of NT and RT from electromagnetic_wave (2007-OCT-8)
definition: electromagnetic radiation
narrower: Cerenkov radiation
narrower: X-ray radiation
narrower: black body radiation
narrower: bremsstrahlung
narrower: continuum radiation
narrower: cyclotron radiation
narrower: gamma-ray radiation
narrower: infrared radiation
narrower: microwave radiation
narrower: millimeter radiation
narrower: polarized light
narrower: polarized radiation
narrower: radio radiation
narrower: submillimeter radiation
narrower: synchrotron radiation
narrower: thermal radiation
narrower: ultraviolet radiation
narrower: visible radiation
related: Planck black body formula
related: color
related: darkness
related: effective temperature
related: electrostatic wave
related: flux density
related: gravitational lensing
related: lamp
related: light absorption
related: light interference
related: light polarization
related: light scattering
related: luminescence
related: photon
related: radiative equilibrium
related: recombination line
related: refraction
related: solar constant
related: wavelength

electromagnetic theory
type: Concept
definition: electromagnetic theory
narrower: cosmic electrodynamics

electron beam
type: Concept
definition: electron beam
narrower: relativistic electron

electron density
type: Concept
broader: density
definition: electron density
related: electron

electron
type: Concept
broader: fundamental particle
broader: lepton
broader: nuclear radiation
broader: particle
definition: electron
related: Compton effect
related: Compton scattering
related: alpha particle
related: bremsstrahlung
related: electron density
related: inverse Compton effect
related: inverse Compton scattering
related: pair annihilation
related: pair production
related: photoionization
related: positron
related: radiative recombination
related: radioactivity
related: recombination
related: thermionic emission

electronic camera
type: Concept
definition: electronic camera
narrower: electronographic camera
related: image tube

electronic equipment
type: Concept
definition: electronic equipment
narrower: diode
related: instrument
related: shot noise

electronics
type: Concept
definition: electronics
scope note: combine with other terms

electronographic camera
type: Concept
alternative label: electrographic camera
broader: electronic camera
definition: electronographic camera

electron pumping
type: Concept
definition: electron pumping
related: laser
related: maser

electron temperature
type: Concept
broader: temperature
definition: electron temperature
history note: APM: new (2007-OCT-4)

electrostatic wave
type: Concept
definition: electrostatic wave
related: electric charge
related: electric field
related: electromagnetic radiation
related: radiation scattering

elementary particle
type: Concept
broader: particle
definition: elementary particle
narrower: antiparticle
narrower: axion
narrower: baryon
narrower: boson
narrower: graviton
narrower: hadron
narrower: lepton
narrower: meson
narrower: neutrino
narrower: neutron
narrower: photon
narrower: pion
narrower: proton
narrower: quark
related: Dark Matter
related: Feynman diagram
related: particle acceleration
related: particle creation
related: particle escape
related: particle interaction
related: particle production
related: plasma
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

elementary particle scattering
type: Concept
broader: scattering
definition: elementary particle scattering
related: radiation scattering

element formation
type: Concept
alternative label: formation of element
definition: element formation
related: abundance
related: chemical element
related: frozen in element
related: origin

ellipsoidal variable star
type: Concept
alternative label: ellipsoidal binary star
alternative label: photometric binary star
broader: binary star
broader: close binary star
broader: contact binary star
broader: variable star
definition: ellipsoidal variable star
narrower: beta Lyrae star
related: eclipsing binary star
related: spectroscopic binary star

elliptical galaxy
type: Concept
alternative label: e galaxy
broader: galaxy
definition: elliptical galaxy
narrower: D galaxy
narrower: E galaxy
narrower: Ep galaxy
narrower: cD galaxy
narrower: giant elliptical galaxy
related: Faber-Jackson relation
related: SBF distance
related: fundamental plane
related: oblateness

elliptical orbit
type: Concept
alternative label: eccentric orbit
broader: orbit
broader: periodic orbit
definition: elliptical orbit
narrower: circular orbit
related: annual equation
related: eccentricity
related: equation of time
related: hyperbolic orbit
related: parabolic orbit

emerging flux
type: Concept
broader: magnetic field
definition: emerging flux
history note: FVH: new (2007-OCT-29)
related: solar activity
related: sunspot

emission coefficient
type: Concept
definition: emission coefficient
related: Einstein coefficient

emission line
type: Concept
broader: spectral line
definition: emission line
narrower: Ca II emission line
narrower: X-ray line
narrower: coronal line
narrower: forbidden line
narrower: recombination line
related: H II region
related: Neumann line
related: atomic process
related: emission line galaxy
related: emission line object
related: emission line star
related: emission nebula
related: emission process
related: emission spectrum
related: flash spectrum
related: line formation
related: line identification
related: line intensitite
related: line profile
related: line ratio
related: spectroscopic analysis
related: spectrum

emission line galaxy
type: Concept
broader: emission line object
broader: galaxy
broader: peculiar galaxy
definition: emission line galaxy
narrower: Markarian galaxy
narrower: Seyfert nucleus
narrower: liner galaxy
related: H II region
related: Haro galaxy
related: Seyfert galaxy
related: active galactic nucleus
related: active galaxy
related: emission line

emission line object
type: Concept
definition: emission line object
narrower: H II region
narrower: Herbig-Haro object
narrower: emission line galaxy
narrower: emission line star
narrower: emission nebula
related: emission line
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

emission line star
type: Concept
broader: active star
broader: emission line object
definition: emission line star
narrower: Me star
narrower: Me variable star
narrower: Mira variable star
narrower: RV Tauri star
narrower: RW Aurigae star
narrower: S Doradus star
narrower: T Tauri star
narrower: X-ray star
narrower: Z Andromedae star
narrower: early-type emission star
narrower: flare star
narrower: flash star
narrower: gamma Cassiopeiae star
narrower: symbiotic star
related: P Cygni line profile
related: U Geminorum star
related: dwarf nova
related: emission line
related: peculiar star
related: planetary nebula
scope note: ES: deleted NT shell_star (2007-OCT-8)

emission nebula
type: Concept
broader: emission line object
broader: gaseous nebula
broader: nebula
definition: emission nebula
narrower: H II region
narrower: Herbig-Haro object
narrower: planetary nebula
related: T Tauri star
related: emission line

emission process
type: Concept
definition: emission process
related: emission line
related: emission spectrum

emission spectrum
type: Concept
broader: line spectrum
broader: spectrum
definition: emission spectrum
narrower: C I emission
narrower: OH emission
narrower: X-ray emission
narrower: free-bound emission
narrower: free-free emission
narrower: infrared emission
narrower: microwave emission
narrower: radio emission
narrower: thermal emission
related: H I emission
related: Neumann line
related: Raman effect
related: emission line
related: emission process
related: light emission

emissivity
type: Concept
definition: emissivity
related: black body radiation
related: radiation
related: temperature

encounter
type: Concept
definition: encounter
narrower: galaxy encounter
related: galaxy merger
related: gravitational interaction
related: stellar dynamics
scope note: generally of star or galaxy

energetic particle
type: Concept
definition: energetic particle
related: plasma

energy content
type: Concept
definition: energy content
scope note: combine with other terms

energy density
type: Concept
broader: density
definition: energy density
history note: FVH: new (2007-OCT-24)
related: Omega Lambda
related: Omega parameter

energy distribution
type: Concept
definition: energy distribution
scope note: combine with other terms

energy
type: Concept
definition: energy
narrower: gravitational energy
narrower: kinetic energy
narrower: potential energy
related: flux
related: force
scope note: combine with other terms

energy level
type: Concept
definition: energy level
related: spectrum

energy source
type: Concept
definition: energy source
scope note: combine with other terms

energy spectrum
type: Concept
definition: energy spectrum
related: absorption spectrum

energy-transfer
type: Concept
alternative label: energy transfer
definition: energy-transfer
narrower: heat-transfer
narrower: radiative transfer
related: adiabatic process
related: conduction
related: convection
related: non-LTE transfer
related: radiation
related: thermodynamic equilibrium
related: thermodynamics

engineering
type: Concept
broader: design
broader: scientific field
definition: engineering
scope note: combine with other terms

English mounting
type: Concept
broader: equatorial mounting
definition: English mounting

enrichment
type: Concept
broader: chemical evolution
definition: enrichment
history note: ES: new (2007-OCT-8)
related: abundance

enthalpy
type: Concept
definition: enthalpy
related: thermodynamics

entropy
type: Concept
definition: entropy
related: thermodynamics

envelope
type: Concept
definition: envelope
related: comet
related: convection
scope note: combine with other terms

Ep galaxy
type: Concept
broader: E galaxy
broader: elliptical galaxy
broader: peculiar galaxy
broader: radio galaxy
definition: peculiar elliptical galaxy with dust absorption (modification of Yerkes classification scheme)
related: Yerkes classification

ephemeral active region
type: Concept
definition: ephemeral active region
related: solar activity

ephemeris
type: Concept
definition: ephemeris
related: almanac
related: calendar
related: catalog
related: fundamental star
related: nautical almanac
related: time

ephemeris time
type: Concept
broader: time
definition: ephemeris time
related: Universal Time
related: civil time
related: mean solar time
related: solar day
related: year

epoch
type: Concept
definition: epoch
narrower: Besselian epoch
narrower: Julian epoch
related: Julian Date
related: time

e-process
type: Concept
definition: e process
related: nuclear fusion
related: stellar evolution
related: supernova

equation of state
type: Concept
definition: equation of state
history note: FVH: new (2007-OCT-8)
related: atomic process
related: interaction

equation of the center
type: Concept
definition: equation of the center
related: Earth-Moon system
related: Moon

equation of the equinox
type: Concept
definition: equation of the equinox
related: Earth rotation
related: equation of time
related: equinox position
related: nutation
related: precession
related: sidereal time

equation of time
type: Concept
definition: equation of time
related: Earth orbit
related: elliptical orbit
related: equation of the equinox
related: mean solar time

equator correction
type: Concept
definition: equator correction
related: celestial equator

equator determination
type: Concept
definition: equator determination
related: celestial equator

equator
type: Concept
definition: equator
related: Declination
related: Right Ascension
related: celestial pole
scope note: of Earth; also see celestial equator

equatorial bulge
type: Concept
definition: equatorial bulge
related: geoid
related: oblateness
related: planet
related: rotation

equatorial coordinate system
type: Concept
alternative label: celestial coordinate
alternative label: equatorial system
broader: celestial coordinate system
definition: equatorial coordinate system
narrower: Declination
narrower: Right Ascension
narrower: celestial equator
narrower: celestial pole
related: equatorial mounting
related: equatorial zone

equatorial mounting
type: Concept
broader: telescope mounting
definition: equatorial mounting
narrower: English mounting
narrower: German mounting
narrower: fork mounting
narrower: horseshoe mounting
narrower: yoke mounting
related: altazimuth mounting
related: equatorial coordinate system

equatorial zone
type: Concept
definition: equatorial zone
related: Declination
related: equatorial coordinate system

equator position
type: Concept
definition: equator position
related: astrometry
related: celestial equator

equilibrium
type: Concept
definition: equilibrium
scope note: combine with other terms

equilibrium figures
type: Concept
definition: equilibrium figures
related: model

equinox correction
type: Concept
definition: equinox correction
related: equinox position

equinox
type: Concept
definition: equinox
narrower: autumnal equinox
narrower: mean equinox
narrower: vernal equinox
related: celestial equator
related: ecliptic
related: solstice

equinox position
type: Concept
definition: equinox position
related: equation of the equinox
related: equinox correction

equipotential surface
type: Concept
definition: equipotential surface
related: contact binary star

equivalent width
type: Concept
broader: line width
definition: equivalent width
related: absorption
related: instrumental profile
related: line broadening
related: spectral line
related: spectrum

erbium
type: Concept
alternative label: Er
broader: fundamental chemical element
broader: rare earth
definition: erbium (atomic number 68)
history note: FVH: new (2007-OCT-25)

e region
type: Concept
broader: Kapteyn selected area
definition: e region
related: Johnson photometry
related: Stromgren photometry
related: photometry

ergosphere
type: Concept
definition: ergosphere
related: black hole
related: event horizon
related: velocity of light

error analysis
type: Concept
broader: data analysis
definition: error analysis
related: data processing
related: data reduction

error
type: Concept
definition: error
narrower: selection effect
related: correction
scope note: combine with other terms

eruption
type: Concept
definition: eruption
related: cataclysmic variable star
related: eruptive binary star

eruptive binary star
type: Concept
broader: binary star
definition: eruptive binary star
narrower: SX Arietis star
narrower: X-ray binary star
narrower: alpha2 Canum Venaticorum star
narrower: cataclysmic variable star
narrower: dwarf nova
narrower: nova
narrower: symbiotic star
related: X-ray source
related: eruption
related: interacting binary star
related: mass exchange
related: mass-loss

escape velocity
type: Concept
broader: velocity
definition: escape velocity
related: orbital velocity
related: parabolic velocity

ethane
type: Concept
broader: hydrocarbon
definition: ethane

ethylene
type: Concept
broader: hydrocarbon
definition: ethylene

europium
type: Concept
alternative label: Eu
broader: fundamental chemical element
broader: rare earth
definition: europium (atomic number 63)
history note: FVH: new (2007-OCT-25)

evaporation
type: Concept
definition: evaporation
scope note: combine with other terms

event horizon
type: Concept
definition: event horizon
related: Hawking radiation
related: black hole
related: ergosphere
related: velocity of light

Evershed-effect
type: Concept
alternative label: Evershed effect
definition: Evershed-effect
related: sunspot

evolutionary track
type: Concept
definition: evolutionary track
narrower: Hayashi track
narrower: Henyey track
related: Hertzsprung-Russell diagram
related: stellar evolution

evolution
type: Concept
definition: evolution
narrower: dynamical evolution
narrower: stellar evolution
related: galaxy
related: planet
scope note: combine with other terms

evolved star
type: Concept
broader: non-main sequence star
broader: star
definition: evolved star
narrower: horizontal branch star
narrower: old star
narrower: planetary nebula
narrower: post-main sequence star
narrower: pulsar
narrower: white dwarf
related: red giant tip
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

excitation
type: Concept
definition: excitation
related: atomic process
scope note: combine with other terms

exciting star
type: Concept
definition: exciting star
related: H II region
related: planetary nebula

exosphere
type: Concept
definition: exosphere
related: Earth atmosphere
related: ionosphere
related: magnetosphere
related: planet
related: thermosphere
related: troposphere
related: upper atmosphere

expanding envelope
type: Concept
broader: circumstellar envelope
definition: expanding envelope
related: circumstellar matter

expanding universe
type: Concept
broader: cosmology
definition: expanding universe

expansion
type: Concept
definition: expansion
scope note: combine with other terms

explosion
type: Concept
definition: explosion
scope note: combine with other terms

exponential profile
type: Concept
broader: mass distribution
definition: exponential mass-profile
history note: FVH: new (2007-OCT-5)
related: Burkert profile
related: Navarro-Frenk-White profile
related: isothermal sphere

extended object
type: Concept
definition: extended object
related: extended source
related: three-dimensional spectrum
related: two-dimensional spectrum

extended source
type: Concept
broader: radio source
broader: source
definition: extended source
related: extended object
related: radio structure

extragalactic object
type: Concept
definition: extragalactic object
narrower: extragalactic radio source
narrower: galaxy
narrower: quasar
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

extragalactic radio source
type: Concept
broader: extragalactic object
broader: radio source
definition: extragalactic radio source
narrower: BL Lacertae object
narrower: quasar
narrower: radio galaxy

extrasolar planet
type: Concept
broader: planet
definition: extrasolar planet
related: Solar System
related: star formation

extraterrestrial intelligence
type: Concept
broader: extraterrestrial life
change note: FVH: moved EXTRATERRESTRIAL_LIFE to BT (2007-OCT-1)
definition: extraterrestrial intelligence
related: search for extraterrestrial life

extraterrestrial life
type: Concept
broader: life
change note: FVH: moved LIFE to BT, SETI to RT (2007-OCT-4)
definition: extraterrestrial life
narrower: extraterrestrial intelligence
related: astrobiology
related: interstellar communication
related: search for extraterrestrial life

extreme carbon star
type: Concept
broader: giant
broader: infrared source
definition: extreme carbon star
related: circumstellar shell

extreme horizontal branch star
type: Concept
broader: horizontal branch star
definition: extreme horizontal branch star
history note: ES: new (2007-OCT-8)

extreme population I star
type: Concept
broader: population I star
definition: extreme population I star

extreme ultraviolet radiation
type: Concept
alternative label: EUV
broader: ultraviolet radiation
definition: extreme ultraviolet radiation
related: far ultraviolet radiation
related: near ultraviolet radiation

eyepiece
type: Concept
definition: eyepiece
narrower: Kellner eyepiece
narrower: Ramsden eyepiece
narrower: orthoscopic eyepiece
related: graticule
related: lens
related: optical telescope
related: reticle

Faber-Jackson distance
type: Concept
broader: distance measurement
definition: Faber-Jackson distance
history note: ES: new (2007-OCT-8)
related: Faber-Jackson relation

Faber-Jackson relation
type: Concept
broader: fundamental plane
broader: luminosity-dispersion relation
broader: statistical relation
definition: Faber-Jackson relation
history note: FVH: new (2007-OCT-9)
related: Faber-Jackson distance
related: elliptical galaxy

Fabry-Perot interferometer
type: Concept
alternative label: Fabry Perot interferometer
broader: interferometer
definition: Fabry-Perot interferometer

Fabry-Perot spectrograph
type: Concept
alternative label: Fabry Perot spectrograph
alternative label: Fabry Perot spectrometer
alternative label: Fabry-Perot spectrometer
broader: spectrograph
definition: Fabry-Perot spectrograph

facula
type: Concept
definition: facula
related: chromosphere
related: granulation
related: photosphere
related: plage

faint blue star
type: Concept
broader: early-type star
broader: faint star
definition: faint blue star

faint galaxy
type: Concept
broader: galaxy
definition: faint galaxy
scope note: combine with other terms

faint star
type: Concept
broader: star
definition: faint star
narrower: faint blue star
scope note: combine with other terms

false color photography
type: Concept
broader: photography
definition: false color photography

Fanaroff-Riley class
type: Concept
definition: fanaroff riley class
related: galaxy
related: radio galaxy

Faraday effect
type: Concept
broader: magneto-optical effect
definition: Faraday effect
definition: Faraday rotation
related: H II region
related: light polarization
related: polarized radiation

far infrared radiation
type: Concept
broader: infrared radiation
definition: far infrared radiation
related: M magnitude
related: N magnitude
related: O magnitude
related: P magnitude
related: Q magnitude
related: infrared photometry
related: near infrared radiation

far ultraviolet radiation
type: Concept
alternative label: FUV
broader: ultraviolet radiation
definition: far ultraviolet radiation
related: extreme ultraviolet radiation
related: near ultraviolet radiation

fast Fourier transform
type: Concept
alternative label: FFT
broader: Fourier transform
definition: fast Fourier transform

fast nova
type: Concept
broader: nova
definition: fast nova
related: recurrent nova
related: slow nova

F corona
type: Concept
alternative label: F component
alternative label: F-corona
broader: corona
definition: F corona
related: zodiacal light

F dwarf
type: Concept
broader: F star
broader: dwarf
definition: F dwarf star

feed
type: Concept
definition: feed
related: feed horn
related: telescope instrument

feed horn
type: Concept
definition: feed horn
related: antenna
related: feed
related: horn antenna
related: radio telescope
related: telescope instrument

Fermi-Dirac nucleus
type: Concept
alternative label: Fermi Dirac nucleus
broader: nucleus atom
definition: Fermi-Dirac nucleus
related: Bose-Einstein nucleus
related: Fermi-Dirac statistics

Fermi-Dirac statistics
type: Concept
alternative label: Fermi Dirac statistics
definition: Fermi-Dirac statistics
related: Bose-Einstein statistics
related: Fermi-Dirac nucleus
related: quantum mechanics

Fermi interaction
type: Concept
broader: weak interaction
definition: Fermi interaction

fermion
type: Concept
broader: fundamental particle
definition: fermion
related: boson

fermium
type: Concept
alternative label: Fm
broader: fundamental chemical element
definition: fermium (atomic number 100)
history note: FVH: new (2007-OCT-25)

Feynman diagram
type: Concept
definition: Feynman diagram
related: elementary particle

Feynman integrals
type: Concept
definition: Feynman integrals

F giant
type: Concept
broader: F star
broader: giant
definition: F giant star

fiber optics
type: Concept
broader: optics
definition: fiber optics
related: optical fiber

fibrill
type: Concept
definition: fibrill
related: chromosphere

field corrector
type: Concept
alternative label: correcting lens
broader: lens
broader: optical component
definition: field corrector
related: catadioptric system
related: corrector plate
related: focal reducer
related: optical instrument

field curvature
type: Concept
alternative label: curvature of field
broader: optical aberration
definition: field curvature
related: astigmatism
related: chromatic aberration
related: comatic aberration
related: distortion
related: optical system
related: spherical aberration

field equation
type: Concept
definition: field equation
related: electromagnetic field
related: relativity

field galaxy
type: Concept
broader: galaxy
definition: field galaxy
scope note: generally, foreground or background object

field of view
type: Concept
definition: field of view
related: vignetting
scope note: at telescope' foci

field star
type: Concept
broader: source
broader: star
definition: field star
scope note: generally, foreground or background object

figuring
type: Concept
broader: polishing
definition: figuring
related: Hartmann test
related: lens
related: mirror
related: optical surface
related: optical testing
scope note: polishing optics to accurate shape

filamentary nebula
type: Concept
broader: nebula
definition: filamentary nebula
related: nebular filament

filling factor
type: Concept
definition: filling factor
related: telescope array

filter
type: Concept
change note: FVH: added NT NEUTRAL_DENSITY_FILTERS (2007-SEP-21)
definition: filter
narrower: interference filter
narrower: neutral density filter
narrower: optical filter
related: attenuation
related: filter wheel

filter wheel
type: Concept
definition: filter wheel
history note: FVH: new (2007-SEP-21)
related: camera
related: filter

finding chart
type: Concept
definition: finding chart
related: atlas
related: map
related: sky survey
related: star atlas

finding list
type: Concept
definition: finding list
related: catalog

fine analysis
type: Concept
broader: analysis
definition: fine analysis
related: data reduction

fine structure
type: Concept
definition: fine structure
related: molecular line
related: spectral line

fireball
type: Concept
broader: meteor
definition: fireball
related: bolide

fission
type: Concept
definition: fission
narrower: nuclear fission

FK catalog system
type: Concept
definition: FK catalog system
related: catalog

flare
type: Concept
alternative label: chromospheric eruption
definition: flare
narrower: X-ray flare
narrower: optical flare
narrower: outburst
narrower: radio flare
related: Sun
related: active Sun
related: burst
related: prominence
related: solar activity
related: solar filament

flare star
type: Concept
broader: dwarf
broader: emission line star
broader: infrared source
broader: radio star
definition: flare star
narrower: BY Draconis star
narrower: UV Ceti star
narrower: red dwarf flare star
related: T association
related: flash star
related: optical flare
related: optical outburst
related: radio flare

flash spectrum
type: Concept
definition: flash spectrum
related: chromosphere
related: emission line
related: solar eclipse

flash star
type: Concept
broader: emission line star
broader: pre-main sequence star
definition: flash star
related: T association
related: UV Ceti star
related: flare star

flat field
type: Concept
definition: flat field
related: image processing
related: two-dimensional detector

flat field lamp
type: Concept
broader: lamp
definition: flat field lamp
history note: FVH: new (2007-SEP-21)
related: calibration
related: camera
related: spectrograph

flattening
type: Concept
definition: flattening
scope note: combine with other terms

F layer
type: Concept
alternative label: F region
definition: F layer
related: Earth atmosphere
related: ionosphere
scope note: Earth upper atmosphere

flexure
type: Concept
definition: flexure
scope note: combine with other terms

florine
type: Concept
alternative label: F
broader: fundamental chemical element
definition: florine (atomic number 9)
history note: FVH: new (2007-OCT-25)

flow
type: Concept
definition: flow
narrower: non-equilibrium flow
related: fluid dynamics
scope note: combine with other terms

flow instability
type: Concept
definition: flow instability
related: non-equilibrium flow

fluctuation
type: Concept
definition: fluctuation
scope note: combine with other terms

fluid dynamics
type: Concept
broader: fluid mechanics
definition: fluid dynamics
narrower: gas dynamics
narrower: hydrodynamics
narrower: relativistic fluid dynamics
related: flow
related: mass-transfer

fluid mechanics
type: Concept
broader: scientific field
definition: fluid mechanics
narrower: fluid dynamics
related: Rayleigh-Taylor instability

fluorescence
type: Concept
definition: fluorescence
narrower: X-ray fluorescence
related: luminescence
related: photoluminescence
related: spectrum

flux density
type: Concept
definition: flux density
related: electromagnetic radiation
related: luminosity
related: radiation

flux
type: Concept
definition: flux
related: energy
related: luminosity
scope note: combine with other terms

focal length
type: Concept
definition: focal length
related: focal reducer
related: focus

focal reducer
type: Concept
definition: focal reducer
related: field corrector
related: focal length

focus
type: Concept
definition: focus
narrower: Cassegrain focus
narrower: Coude focus
narrower: Nasmyth focus
narrower: Newtonian focus
narrower: prime focus
related: focal length
related: optical aberration
related: telescope

Fokker-Planck equation
type: Concept
alternative label: Fokker Planck equation
definition: Fokker-Planck equation
related: stellar dynamics

forbidden line
type: Concept
broader: emission line
definition: forbidden line
related: forbidden transition
related: nebula
related: spectrum

forbidden transition
type: Concept
definition: forbidden transition
related: forbidden line
related: nebula
related: spectrum

forbush effect
type: Concept
definition: forbush effect
related: cosmic ray
related: solar physics

force
type: Concept
definition: force
narrower: centrifugal force
narrower: centripetal force
narrower: electromagnetic forces
narrower: gravitational force
related: electric field
related: energy
related: magnetic field
scope note: combine with other terms

forecasts
type: Concept
definition: forecasts
related: prediction
scope note: combine with other terms

fork mounting
type: Concept
broader: equatorial mounting
definition: fork mounting

formation
type: Concept
definition: formation
scope note: combine with other terms

Fourier analysis
type: Concept
alternative label: harmonic analysis
definition: Fourier analysis
related: Fourier component
related: Fourier transform
related: fundamental frequency
related: harmonic frequency
related: maximum entropy method
related: multi-periodic pulsation
related: overtone frequency
related: waveform analysis

Fourier component
type: Concept
definition: Fourier component
related: Fourier analysis
related: harmonic frequency

Fourier spectrograph
type: Concept
alternative label: Fourier spectrometer
broader: spectrograph
definition: Fourier spectrograph

Fourier transform
type: Concept
definition: Fourier transform
narrower: fast Fourier transform
related: Fourier analysis

Fourier transform spectroscopy
type: Concept
broader: spectroscopy
definition: Fourier transform spectroscopy

fragmentation
type: Concept
definition: fragmentation
scope note: combine with other terms

fragment
type: Concept
definition: fragment
scope note: combine with other terms

francium
type: Concept
alternative label: Fr
broader: fundamental chemical element
definition: francium (atomic number 87)
history note: FVH: new (2007-OCT-25)

Fraunhofer line
type: Concept
broader: spectral line
definition: Fraunhofer line
narrower: B band
narrower: G band
narrower: H line
narrower: K line
related: Sun
related: absorption spectrum
scope note: not a complete list of terms

free-bound emission
type: Concept
alternative label: free bound emission
broader: emission spectrum
broader: radiation mechanism
definition: free-bound emission

free-free emission
type: Concept
alternative label: free free emission
broader: emission spectrum
broader: radiation mechanism
definition: free-free emission
related: spectrum
related: thermal emission

f region
type: Concept
broader: Kapteyn selected area
definition: f region
related: Johnson photometry
related: Stromgren photometry
related: photometry

frequency analysis
type: Concept
definition: frequency analysis
related: maximum entropy method
related: multi-periodic pulsation

frequency distribution
type: Concept
definition: frequency distribution
related: Hess diagram
related: distribution function

frequency
type: Concept
definition: frequency
related: wavelength
scope note: combine with other terms

frequency shift
type: Concept
definition: frequency shift
narrower: glitch
related: blueshift
related: pulsar
related: redshift

frequency standard
type: Concept
definition: frequency standard
related: instrument

friction
type: Concept
definition: friction
narrower: dynamical friction

Friedmann universe
type: Concept
broader: cosmology
definition: Friedmann universe
related: Big Bang theory
related: oscillating universe

frozen in element
type: Concept
definition: frozen in element
related: element formation
related: supernova

F star
type: Concept
broader: intermediate type star
definition: F star
narrower: F dwarf
narrower: F giant
narrower: F subdwarf
narrower: F subgiant
narrower: F supergiant
related: spectral type

F subdwarf
type: Concept
broader: F star
broader: subdwarf
definition: F subdwarf star

F subgiant
type: Concept
broader: F star
broader: subgiant
definition: F subgiant star

F supergiant
type: Concept
broader: F star
broader: supergiant
definition: F supergiant star
narrower: UU Herculis star

function
type: Concept
definition: function
narrower: distribution function
scope note: in mathematics

fundamental chemical element
type: Concept
broader: atom
broader: chemical element
definition: the fundamental chemical element which appear in the periodic table
history note: FVH: new (2007-OCT-25)
narrower: actinium
narrower: aluminum
narrower: americium
narrower: antimony
narrower: argon
narrower: arsenic
narrower: astatine
narrower: barium
narrower: berkelium
narrower: beryllium
narrower: bismuth
narrower: bohrium
narrower: boron
narrower: bromine
narrower: cadmium
narrower: caesium
narrower: calcium
narrower: californium
narrower: carbon
narrower: cerium
narrower: chlorine
narrower: chromium
narrower: cobalt
narrower: copper
narrower: curium
narrower: darmtadtium
narrower: dubnium
narrower: dysprosium
narrower: einsteinium
narrower: erbium
narrower: europium
narrower: fermium
narrower: florine
narrower: francium
narrower: gadolinium
narrower: gallium
narrower: germanium
narrower: gold
narrower: hafnium
narrower: hassium
narrower: helium
narrower: holmium
narrower: hydrogen
narrower: indium
narrower: iodine
narrower: iridium
narrower: iron
narrower: krypton
narrower: lanthanum
narrower: lawrencium
narrower: lead
narrower: lithium
narrower: lutetium
narrower: magnesium
narrower: manganese
narrower: meitnerium
narrower: mendelevium
narrower: mercury
narrower: molybdenum
narrower: neodymium
narrower: neon
narrower: neptunium
narrower: nickel
narrower: niobium
narrower: nitrogen
narrower: nobelium
narrower: osmium
narrower: oxygen
narrower: palladium
narrower: phosphorus
narrower: platinum
narrower: plutonium
narrower: polonium
narrower: potassium
narrower: praseodymium

fundamental frequency
type: Concept
definition: fundamental frequency
related: Fourier analysis
related: fundamental mode
related: harmonic frequency
related: overtone frequency
related: variable star

fundamental mode
type: Concept
broader: pulsation mode
definition: fundamental mode
related: fundamental frequency
related: overtone mode

fundamental particle
type: Concept
broader: particle
definition: fundamental particle
narrower: electron
narrower: fermion
narrower: neutron
narrower: proton

fundamental plane
type: Concept
broader: luminosity-dispersion relation
broader: radius-luminosity relation
definition: fundamental plane
history note: FVH: new (2007-OCT-9)
narrower: Faber-Jackson relation
related: elliptical galaxy

fundamental star
type: Concept
broader: star
definition: fundamental star
related: astrometry
related: catalog
related: ephemeris

fundamental system
type: Concept
definition: fundamental system
related: position
scope note: combine with other terms

funneling
type: Concept
definition: funneling
related: late-type giant
related: stellar evolution

FU Orionis star
type: Concept
broader: T Tauri star
broader: infrared source
definition: fu orionis star
related: T association
related: mass-loss

fusion
type: Concept
definition: fusion
narrower: nuclear fusion

future light cone
type: Concept
broader: light cone
definition: future light cone
related: past light cone

gadolinium
type: Concept
alternative label: Gd
broader: fundamental chemical element
broader: rare earth
definition: gadolinium (atomic number 64)
history note: FVH: new (2007-OCT-25)

Galactic
type: Concept
definition: Galactic
scope note: FVH: WARNING: usage is not consistent when combined within tokens, e.g. galactic_nucleus (the MW has only one!), so capitalized (2007-OCT-5)
scope note: IAU: used as an adjective only for Milky Way property see also galaxy

Galactic anticenter
type: Concept
alternative label: anticenter
change note: FVH: capitalized, since only refers to MW (2007-OCT-5)
definition: Galactic anticenter
related: Galactic coordinate system
related: Milky Way galaxy

Galactic bulge
type: Concept
broader: bulge
change note: FVH: capitalized, since only refers to MW; added BT bulge (2007-OCT-5)
definition: Galactic bulge (Milky Way)
related: Galactic center
related: Galactic plane
related: Galactic structure
related: Milky Way galaxy

Galactic center
type: Concept
broader: galactic nucleus
change note: FVH: capitalized, since only refers to MW; added BT galactic_nucleus (2007-OCT-5)
definition: Galactic center (Milky Way)
related: Galactic bulge
related: Galactic coordinate system
related: Galactic structure
related: Milky Way galaxy

Galactic cluster
type: Concept
broader: open star cluster
change note: FVH: capitalized, since only refers to MW (2007-OCT-5)
definition: Galactic open star cluster (in Milky Way)
related: Milky Way galaxy

Galactic coordinate system
type: Concept
broader: celestial coordinate system
change note: FVH: capitalized, since only refers to MW (2007-OCT-5)
definition: Galactic coordinate system
related: Galactic anticenter
related: Galactic center
related: Galactic latitude
related: Galactic longitude
related: Galactic pole
related: Milky Way galaxy

Galactic cosmic ray
type: Concept
broader: cosmic ray
change note: FVH: capitalized, since only refers to MW; moved cosmic_ray to BT (2007-OCT-5)
definition: Galactic cosmic ray
related: Milky Way galaxy

Galactic equator
type: Concept
change note: FVH: capitalized, since only refers to MW (2007-OCT-5)
definition: Galactic equator
related: Galactic latitude
related: Galactic longitude
related: Galactic pole
related: Milky Way galaxy

Galactic halo
type: Concept
broader: halo
change note: FVH: added RT POPULATION_III_STARS (2007-SEP-21)
change note: FVH: capitalized, since only refers to MW (2007-OCT-5)
definition: Galactic halo
related: Galactic structure
related: Milky Way galaxy
related: RR Lyrae star
related: globular star cluster
related: halo star
related: population II star
related: population III star

Galactic latitude
type: Concept
broader: latitude
change note: FVH: capitalized, since only refers to MW; moved latitude to BT (2007-OCT-5)
definition: Galactic latitude
related: Galactic coordinate system
related: Galactic equator
related: Galactic longitude
related: Galactic plane
related: Galactic pole
related: Milky Way galaxy

Galactic longitude
type: Concept
broader: longitude
change note: FVH: capitalized, since only refers to MW; moved longitude to BT (2007-OCT-5)
definition: Galactic longitude
related: Galactic coordinate system
related: Galactic equator
related: Galactic latitude
related: Galactic pole
related: Milky Way galaxy

galactic nucleus
type: Concept
broader: nucleus celestial object
definition: galactic nucleus
narrower: Galactic center
narrower: active galactic nucleus
narrower: compact nucleus
related: Galactic structure
related: N galaxy
related: black hole
related: galaxy structure
related: massive object
related: population II star

Galactic plane
type: Concept
change note: FVH: capitalized, since only refers to MW (2007-OCT-5)
definition: Galactic plane (Milky Way)
related: Galactic bulge
related: Galactic latitude
related: Galactic pole
related: Galactic window
related: Milky Way galaxy
related: disk population
related: disk star

Galactic pole
type: Concept
broader: pole
change note: FVH: capitalized, since only refers to MW (2007-OCT-5)
definition: Galactic pole (Milky Way)
narrower: North Galactic Pole
narrower: South Galactic Pole
related: Galactic coordinate system
related: Galactic equator
related: Galactic latitude
related: Galactic longitude
related: Galactic plane
related: Galactic spurs
related: Milky Way galaxy

Galactic rotation
type: Concept
broader: galaxy rotation curve
broader: rotation
change note: FVH: capitalized, since only refers to MW (2007-OCT-5)
change note: see galaxy_rotation_curve for external galaxy
definition: Galactic rotation (Milky Way)
related: Dark Matter
related: Milky Way galaxy
related: Oort constant
related: Oort formulae
related: cosmic year
related: differential rotation
related: high-velocity cloud
related: high-velocity star
related: kinematics
related: proper motion
related: space motion
related: stellar dynamics

Galactic spurs
type: Concept
change note: FVH: capitalized, since only refers to MW (2007-OCT-5)
definition: Galactic spurs (Milky Way)
related: Galactic pole
related: Galactic structure

Galactic structure
type: Concept
broader: galaxy structure
change note: FVH: capitalized, since only refers to MW; added BT galaxy_structure (2007-OCT-5)
definition: Galactic structure (Milky Way)
related: Galactic bulge
related: Galactic center
related: Galactic halo
related: Galactic spurs
related: Oort constant
related: Oort formulae
related: galactic nucleus
related: kinematics
related: pitch angle
related: spiral arm
related: star count
scope note: See galaxy_structure for generic term (2007-OCT-5; FVH)

Galactic window
type: Concept
broader: window
change note: FVH: capitalized, since only refers to MW (2007-OCT-5)
change note: direction of low absorption
definition: Galactic window (Milky Way)
related: Galactic plane
related: interstellar absorption

galaxy cluster
type: Concept
alternative label: cluster of galaxies
alternative label: galaxy clustering
broader: cluster
definition: cluster of galaxies
narrower: Abell cluster
narrower: Local Supercluster
related: Great Attractor
related: Sunyaev-Zeldovich effect
related: cD galaxy
related: clustering
related: galaxy count
related: galaxy distribution
related: galaxy merger
related: intergalactic matter
related: intracluster matter
related: luminosity function
related: luminous arc
related: mass distribution
related: massive galaxy
related: missing mass
related: multiple galaxy
related: protocluster
related: relaxation time
related: supercluster
related: supergalactic coordinate system
related: velocity dispersion
related: velocity distribution
related: virial theorem

galaxy content
type: Concept
definition: galaxy content
scope note: combine with other terms

galaxy count
type: Concept
definition: galaxy count
related: Dark Energy
related: cosmology
related: galaxy cluster
related: galaxy distribution
related: observational cosmology

galaxy distribution
type: Concept
definition: galaxy distribution
related: Dark Energy
related: cosmology
related: galaxy cluster
related: galaxy count
related: observational cosmology

galaxy encounter
type: Concept
broader: encounter
definition: galaxy encounter
related: galaxy merger
related: interacting galaxy
related: radio source

galaxy evolution
type: Concept
definition: galaxy evolution
related: cosmology

galaxy formation
type: Concept
alternative label: formation of galaxies
definition: galaxy formation

galaxy
type: Concept
broader: extragalactic object
broader: rotating body
definition: galaxy
narrower: BL Lacertae object
narrower: D galaxy
narrower: Haro galaxy
narrower: L galaxy
narrower: Magellanic cloud
narrower: Milky Way galaxy
narrower: N galaxy
narrower: active galaxy
narrower: barred spiral galaxy
narrower: bipolar galaxy
narrower: blue galaxy
narrower: bright galaxy
narrower: companion galaxy
narrower: disk galaxy
narrower: double galaxy
narrower: dwarf galaxy
narrower: early-type galaxy
narrower: elliptical galaxy
narrower: emission line galaxy
narrower: faint galaxy
narrower: field galaxy
narrower: giant galaxy
narrower: head tail galaxy
narrower: hypergalaxy
narrower: infrared galaxy
narrower: interacting galaxy
narrower: irregular galaxy
narrower: late-type galaxy
narrower: lenticular galaxy
narrower: massive galaxy
narrower: multiple galaxy
narrower: nearby galaxy
narrower: peculiar galaxy
narrower: primordial galaxy
narrower: protogalaxy
narrower: radio galaxy
narrower: ring galaxy
narrower: spiral galaxy
narrower: starburst galaxy
related: Fanaroff-Riley class
related: Holmberg radius
related: Hubble classification
related: Hubble diagram
related: Local Supercluster
related: Tully-Fisher relation
related: Yerkes classification
related: active galactic nucleus
related: collision
related: coma
related: cooling flow
related: differential rotation
related: edge effect
related: evolution
related: galaxy structure
related: halo
related: integrated magnitude
related: isophotal diameter
related: luminosity function
related: mass distribution
related: mass to light ratio
related: origin
related: quasar galaxy pair
related: surface photometry
related: velocity field

galaxy group
type: Concept
definition: group of galaxies
narrower: Hickson compact group
narrower: Local Group
related: companion galaxy
related: multiple galaxy

galaxy merger
type: Concept
broader: merger
definition: galaxy merger
related: double galaxy
related: encounter
related: galaxy cluster
related: galaxy encounter
related: interacting galaxy

galaxy rotation curve
type: Concept
broader: rotation
change note: FVH: since Galactic_rotation only refers to MW (2007-OCT-5)
definition: rotation curve of galaxy
narrower: Galactic rotation
related: Dark Matter
related: differential rotation
related: galaxy structure
related: kinematics
related: mass distribution
related: stellar dynamics

galaxy structure
type: Concept
alternative label: content of galaxy
alternative label: structure of galaxy
broader: structure
change note: FVH: new, since Galactic_structure only refers to Milky Way; moved content_of_galaxy to ALT (2007-OCT-5)
change note: FVH: renamed galaxy_structure to remove _of_ (2007-OCT-24)
definition: structure of galaxy
narrower: Galactic structure
related: bulge
related: galactic nucleus
related: galaxy
related: galaxy rotation curve
related: halo
related: interstellar matter
related: kinematics
related: mass distribution
related: pitch angle
related: spiral arm

galaxy void
type: Concept
definition: galaxy void
related: blank field
related: intergalactic space

galilean satellite
type: Concept
broader: satellite
definition: galilean satellite
related: planet

gallium
type: Concept
alternative label: Ga
broader: fundamental chemical element
definition: gallium (atomic number 31)
history note: FVH: new (2007-OCT-25)

gamma Cassiopeiae star
type: Concept
broader: B dwarf
broader: emission line star
broader: irregular variable star
broader: shell star
definition: gamma Cassiopeiae star

gamma-ray astronomy
type: Concept
alternative label: gamma ray astronomy
broader: space astronomy
definition: gamma-ray astronomy
related: balloon-borne instrument
related: rocket-borne instrument
related: satellite-borne instrument

gamma-ray background
type: Concept
alternative label: gamma ray background
broader: background radiation
definition: gamma-ray background
related: X-ray background
related: gamma-ray radiation
related: microwave background
related: radio background
related: ultraviolet background

gamma-ray burst
type: Concept
alternative label: GRB
alternative label: cosmic gamma ray burst
alternative label: cosmic gamma-ray burst
alternative label: gamma ray burst
broader: burst
definition: gamma-ray burst
related: X-ray burst
related: burster
related: gamma-ray source
related: hypernova
related: optical burst
related: radio burst
related: rapid burst

gamma-ray line
type: Concept
alternative label: gamma ray line
broader: gamma-ray radiation
change note: FVH: moved RT gamma-ray to BT gamma-ray_radiation (2007-OCT-8)
definition: gamma-ray line

gamma-ray observatory
type: Concept
alternative label: gamma ray observatory
broader: observatory
broader: space observatory
definition: gamma-ray observatory
related: gamma-ray telescope
scope note: see observatory for more rts

gamma-ray radiation
type: Concept
alternative label: gamma radiation
alternative label: gamma-ray
broader: electromagnetic radiation
broader: high-energy radiation
broader: nuclear radiation
broader: radiation
definition: gamma-ray radiation
narrower: gamma-ray line
related: Cerenkov radiation
related: gamma-ray background
related: gamma-ray scattering
related: gamma-ray source
related: gamma-ray spectrum
related: pair annihilation
related: pair production
related: radioactivity

gamma-ray scattering
type: Concept
alternative label: gamma ray scattering
broader: scattering
definition: gamma-ray scattering
related: gamma-ray radiation

gamma-ray source
type: Concept
alternative label: gamma ray source
broader: source
definition: gamma-ray source
narrower: soft gamma-ray repeater
related: gamma-ray burst
related: gamma-ray radiation
related: optical identification

gamma-ray spectrograph
type: Concept
alternative label: gamma ray spectrograph
broader: spectrograph
definition: gamma-ray spectrograph

gamma-ray spectroscopy
type: Concept
broader: spectroscopy
definition: gamma-ray spectroscopy
related: gamma-ray spectrum

gamma-ray spectrum
type: Concept
alternative label: gamma ray spectrum
definition: gamma-ray spectrum
related: gamma-ray radiation
related: gamma-ray spectroscopy

gamma-ray telescope
type: Concept
broader: space telescope
broader: telescope
definition: gamma-ray telescope
related: gamma-ray observatory

gas cloud
type: Concept
broader: cloud
definition: gas cloud

gas content
type: Concept
definition: gas content
related: gas

gas density
type: Concept
broader: density
definition: gas density
related: gas
related: optical depth

gas distribution
type: Concept
definition: gas distribution
related: gas
related: spiral arm

gas dynamics
type: Concept
alternative label: gas kinematics
broader: fluid dynamics
definition: gas dynamics
related: gas

gaseous disk
type: Concept
broader: disk
definition: gaseous discs UK
definition: gaseous disk
related: disk star
related: gas

gaseous nebula
type: Concept
broader: nebula
definition: gaseous nebula
narrower: emission nebula
related: gas

gaseous sphere
type: Concept
definition: gaseous sphere
narrower: Stromgren sphere
narrower: protogalaxy
narrower: protostar
related: gas

gas
type: Concept
definition: gas
narrower: air
narrower: carbon dioxide
narrower: carbon monoxide
narrower: ionized gas
narrower: neutral gas
narrower: relativistic plasma
related: gas content
related: gas density
related: gas distribution
related: gas dynamics
related: gas to dust ratio
related: gaseous disk
related: gaseous nebula
related: gaseous sphere
scope note: See also table of elements
scope note: combine with other terms

gas to dust ratio
type: Concept
definition: gas to dust ratio
related: dust
related: gas
related: interstellar reddening
related: reddening law
related: selective absorption

G band
type: Concept
broader: Fraunhofer line
broader: molecular band
definition: G-band
related: molecular spectrum

G dwarf
type: Concept
broader: G star
broader: dwarf
definition: G dwarf star

gegenschein
type: Concept
alternative label: counterglow
definition: gegenschein
related: interplanetary matter
related: night sky brightness
related: zodiacal dust
related: zodiacal light

general theory of relativity
type: Concept
broader: gravitation
broader: relativity
definition: general theory of relativity
narrower: special theory of relativity
related: Dark Energy
related: Newtonian gravitation
related: Schwarzschild metric
related: Schwarzschild radius
related: cosmology
related: gravitational effect
related: gravitational wave
related: space
related: space-time curvature
related: time

Geneva photometry
type: Concept
alternative label: ubvgri photometry
broader: medium band photometry
broader: photometric system
definition: Geneva photometry
related: Vilnius photometry

geocentric orbit
type: Concept
broader: orbit
definition: geocentric orbit

geocorona
type: Concept
definition: geocorona
related: Earth

geodesy
type: Concept
broader: Earth sciences
definition: geodesy
narrower: astronomical geodesy
narrower: space geodesy
related: Earth
related: atomic clock
related: geoid
related: pendulum

geoid
type: Concept
definition: geoid
related: Earth
related: equatorial bulge
related: geodesy

geology
type: Concept
broader: Earth sciences
definition: geology
narrower: petrology
related: geophysical observatory
related: glaciology
related: planet
related: planetology
related: surface of celestial body

geomagnetic field
type: Concept
broader: magnetic field
definition: geomagnetic field

geomagnetism
type: Concept
definition: geomagnetism
related: Earth
related: continental drift
related: geophysical observatory
related: paleomagnetism
related: planet

geophysical observatory
type: Concept
broader: observatory
definition: geophysical observatory
related: Earth sciences
related: geology
related: geomagnetism
scope note: see observatory for more rts

geophysics
type: Concept
alternative label: terrestrial physics
broader: Earth sciences
definition: geophysics
related: Earth
related: continental drift

geostationary satellite
type: Concept
broader: artificial satellite
definition: geostationary satellite

germanium
type: Concept
alternative label: Ge
broader: fundamental chemical element
definition: germanium (atomic number 32)
history note: FVH: new (2007-OCT-25)

German mounting
type: Concept
broader: equatorial mounting
definition: German mounting

gf value
type: Concept
definition: gf value
related: g value
related: line formation
related: line width
related: log g value
related: oscillator strength
related: transition probability

G giant
type: Concept
broader: G star
broader: giant
definition: G giant star
related: G subgiant

giant branch
type: Concept
alternative label: RGB
alternative label: red giant branch
definition: giant branch
narrower: blue loop
narrower: red giant bump
narrower: red giant clump
narrower: red giant tip
related: Hertzsprung gap
related: Hertzsprung-Russell diagram
related: instability strip
related: turnoff point
related: zero-age horizontal branch

giant branch star
type: Concept
broader: star
definition: giant branch star
related: horizontal branch star

giant elliptical galaxy
type: Concept
broader: elliptical galaxy
definition: giant elliptical galaxy

giant galaxy
type: Concept
broader: galaxy
definition: giant galaxy
narrower: cD galaxy

giant
type: Concept
alternative label: CS star
broader: post-main sequence star
definition: giant star
narrower: A giant
narrower: B giant
narrower: CH star
narrower: CN star
narrower: F giant
narrower: G giant
narrower: Lb variable star
narrower: M giant
narrower: OH IR star
narrower: R star
narrower: S star
narrower: extreme carbon star
narrower: late-type giant
narrower: peculiar giant
narrower: weak G band star
related: carbon burning
related: dredge up
related: lithium star
related: luminosity classification
related: stellar evolution
related: zirconium star

giant molecular cloud
type: Concept
broader: molecular cloud
definition: giant molecular cloud
related: interstellar molecule

giant planet
type: Concept
broader: planet
definition: giant planet

giant radio galaxy
type: Concept
broader: radio galaxy
definition: giant radio galaxy
related: N galaxy
related: cD galaxy

glaciology
type: Concept
broader: Earth sciences
definition: glaciology
related: Earth
related: geology

glass
type: Concept
broader: optical material
definition: glass
narrower: optical glass
related: lens
related: mirror
related: optical fiber

glitch
type: Concept
broader: frequency shift
definition: sudden frequency shift
history note: FVH: new (2007-OCT-8)
related: pulsar

global positioning system
type: Concept
alternative label: GPS
definition: Global Positioning System
related: satellite
related: time signal
related: time standard
related: time synchronization

globular star cluster
type: Concept
broader: star cluster
definition: globular star cluster
related: Galactic halo
related: Oosterhoff group
related: RR Lyrae star
related: differential rotation
related: halo star
related: horizontal branch star
related: population II star
related: population III star
related: turnoff point

globule
type: Concept
broader: interstellar matter
definition: globule
narrower: Bok globule
narrower: cometary globule
related: dark nebula

Goedel universe
type: Concept
broader: cosmology
definition: Goedel universe

gold
type: Concept
alternative label: Au
broader: fundamental chemical element
definition: gold (atomic number 79)
history note: FVH: new (2007-OCT-25)

Goulds belt
type: Concept
definition: Goulds belt
related: Milky Way galaxy
related: star association

grading function
type: Concept
alternative label: illumination function
definition: grading function
related: aperture synthesis

grain
type: Concept
broader: interstellar matter
definition: grain
narrower: interplanetary grain
related: interplanetary dust
related: interstellar dust

granulation
type: Concept
definition: granulation
narrower: supergranulation
related: Sun
related: convection
related: facula
related: photosphere

granule
type: Concept
definition: granule
related: Sun
related: photosphere

graph
type: Concept
definition: graph
scope note: combine with other terms

graphite
type: Concept
definition: graphite
related: interplanetary grain
related: interstellar dust

graticule
type: Concept
definition: graticule
related: eyepiece
related: reticle

grating response
type: Concept
definition: grating response
related: array

grating ring
type: Concept
definition: grating ring
related: aperture synthesis

grating spectrograph
type: Concept
broader: spectrograph
definition: grating spectrograph
related: diffraction grating
related: prism spectrograph

gravimetry
type: Concept
definition: gravimetry
related: acceleration

gravitating disk
type: Concept
broader: disk
definition: gravitating discs UK
definition: gravitating disk
related: circumstellar matter

gravitational collapse
type: Concept
broader: collapse
definition: gravitational collapse
related: Chandrasekhar mass
related: Chandrasekhar-Schoenberg limit
related: black hole
related: gravitation
related: gravitational energy
related: supernova

gravitational constant
type: Concept
broader: physical constant
definition: Newton's gravitational constant G
related: Newtonian gravitation

gravitational deflection
type: Concept
definition: gravitational deflection
related: Einstein ring
related: double quasar
related: gravitational lensing

gravitational effect
type: Concept
definition: gravitational effect
related: MOdified Newtonian Dynamics
related: general theory of relativity

gravitational energy
type: Concept
broader: energy
definition: gravitational energy
related: gravitational collapse

gravitational equilibrium
type: Concept
definition: gravitational equilibrium
related: stellar evolution

gravitational field
type: Concept
alternative label: gravity field
definition: gravitational field
related: Lagrangian point
related: Schwarzschild metric
related: quantum field theory

gravitational force
type: Concept
alternative label: force of gravity
broader: force
definition: gravitational force
related: Eddington limit
related: MOdified Newtonian Dynamics
related: Newtonian gravitation
related: gravitation
related: surface gravity

gravitational instability
type: Concept
definition: gravitational instability
related: gravitation

gravitational interaction
type: Concept
broader: interaction
definition: gravitational interaction
related: encounter
related: gravitation

gravitational lens
type: Concept
change note: FVH: effectively new, since old IAU term moved to gravitational_lensing (2007-OCT-08)
definition: gravitational lens
scope note: refers to the lens themselves, not the lensing process (see gravitational_lensing)

gravitational lensing
type: Concept
change note: FVH: removed RT white_hole, added NT gravitational_microlensing etc. (2007-OCT-8)
definition: gravitational lensing
narrower: gravitational lensing shear
narrower: gravitational microlensing
narrower: strong gravitational lensing
narrower: weak gravitational lensing
related: Einstein ring
related: black hole
related: caustic
related: caustic crossing
related: cusp
related: cusp crossing
related: double quasar
related: electromagnetic radiation
related: gravitation
related: gravitational deflection
related: gravitationally lensed source
related: luminous arc
related: mass distribution
related: visible radiation
related: white hole

gravitational lensing shear
type: Concept
broader: gravitational lensing
definition: gravitational lensing shear
history note: FVH: new (2007-OCT-8)

gravitationally lensed source
type: Concept
broader: source
definition: gravitationally lensed source
history note: FVH: new (2007-OCT-8)
narrower: Einstein ring
narrower: double quasar
narrower: luminous arc
related: gravitational lensing

gravitational microlensing
type: Concept
alternative label: microlensing
broader: gravitational lensing
change note: FVH: added gravitational_ as prefix; moved RT to BT gravitational_lensing (2007-OCT-8)
definition: microlensing
narrower: planetary microlensing
narrower: quasar microlensing

gravitational radiation
type: Concept
broader: radiation
definition: gravitational radiation
related: gravitation
related: radiation mechanism

gravitational redshift
type: Concept
broader: redshift
definition: gravitational redshift
related: Einstein effect
related: gravitation

gravitational wave
type: Concept
broader: wave
definition: gravitational wave
related: celestial mechanics
related: general theory of relativity

gravitation
type: Concept
definition: gravitation
narrower: MOdified Newtonian Dynamics
narrower: Newtonian gravitation
narrower: general theory of relativity
related: Lagrangian point
related: Roche limit
related: celestial mechanics
related: gravitational collapse
related: gravitational force
related: gravitational instability
related: gravitational interaction
related: gravitational lensing
related: gravitational radiation
related: gravitational redshift
related: gravity
related: mass
related: perturbation theory
related: relativity
related: virial theorem

graviton
type: Concept
broader: elementary particle
definition: graviton

gravity anomaly
type: Concept
broader: anomaly
definition: gravity anomaly
related: magnetic anomaly
related: mascon

gravity darkening
type: Concept
definition: gravity darkening
related: surface brightness
related: surface gravity
related: von Zeipel theorem

gravity
type: Concept
alternative label: acceleration of gravity
definition: gravity
related: Jeans length
related: gravitation
related: pendulum
related: relativistic astrophysics
related: von Zeipel theorem

gravity wave
type: Concept
broader: wave
definition: gravity wave
related: acoustic wave
related: stellar interior

grazing incidence
type: Concept
definition: grazing incidence
scope note: combine with other terms

grazing incidence spectrograph
type: Concept
broader: spectrograph
definition: grazing incidence spectrograph
narrower: X-ray spectrograph

grazing incidence telescope
type: Concept
broader: telescope
definition: grazing incidence telescope
narrower: X-ray telescope

Great Attractor
type: Concept
definition: Great Attractor
related: Local Supercluster
related: galaxy cluster

greenhouse effect
type: Concept
definition: greenhouse effect
related: atmosphere
related: infrared radiation
related: planet
related: pollution
related: terrestrial radiation

Gregorian calendar
type: Concept
broader: calendar
definition: Gregorian calendar
related: Julian calendar
related: time

Gregorian telescope
type: Concept
broader: telescope
definition: Gregorian telescope

grid
type: Concept
definition: grid
related: reseaux
related: reticle

grism
type: Concept
broader: optical component
definition: grism
related: diffraction grating
related: prism
related: spectrograph
related: transmission grating

ground-based astronomy
type: Concept
alternative label: ground based astronomy
broader: astronomy
definition: ground-based astronomy
related: airplane-borne instrument
related: balloon-borne instrument
related: rocket-borne instrument
related: satellite-borne instrument
related: space probe instrument
related: space telescope

G star
type: Concept
broader: intermediate type star
definition: G star
narrower: G dwarf
narrower: G giant
narrower: G subdwarf
narrower: G subgiant
narrower: G supergiant
related: spectral type

G subdwarf
type: Concept
broader: G star
broader: subdwarf
definition: G subdwarf star

G subgiant
type: Concept
broader: G star
broader: subgiant
definition: G subgiant star
related: G giant

G supergiant
type: Concept
broader: G star
broader: supergiant
definition: G supergiant star

guide system
type: Concept
broader: instrument
definition: guide system
narrower: autoguider
related: control system
related: quadrant detector
related: telescope

Gunn diode
type: Concept
definition: Gunn diode
related: semiconductor device

Gunn photometry
type: Concept
alternative label: Gunn g,r,i,z photometry
broader: broad band photometry
broader: photometric system
definition: Gunn photometry
history note: FVH: new (2007-SEP-21)

g value
type: Concept
definition: g value
narrower: log g value
related: gf value
related: line formation
related: line width
related: oscillator strength
related: transition probability

gyrosynchrotron radiation
type: Concept
broader: synchrotron radiation
definition: gyrosynchrotron radiation

hadron barrier
type: Concept
definition: hadron barrier
related: Big Bang theory

hadron
type: Concept
broader: elementary particle
definition: hadron
related: boson

hafnium
type: Concept
alternative label: Hf
broader: fundamental chemical element
definition: hafnium (atomic number 72)
history note: FVH: new (2007-OCT-25)

halation
type: Concept
definition: halation
related: image
related: photographic emulsion
related: turbidity

half-wave dipole
type: Concept
alternative label: half wave dipole
alternative label: halfwave dipole
broader: dipole
definition: half-wave dipole
related: Yagi antenna
related: radio telescope

half-wave plate
type: Concept
alternative label: half wave plate
alternative label: halfwave plate
definition: half-wave plate
history note: FVH: new (2007-SEP-21)
related: plane polarization
related: quarter wave plate

halo
type: Concept
definition: halo
narrower: Galactic halo
related: comet
related: corona
related: galaxy
related: galaxy structure
related: halo star
related: light scattering

halo star
type: Concept
broader: population II star
broader: population III star
broader: star
definition: halo star
related: Galactic halo
related: globular star cluster
related: halo
related: stellar population

H alpha
type: Concept
broader: Balmer series
broader: resonance line
definition: H alpha (656 nm)
related: H alpha emission line star
related: H alpha photometry

H alpha emission line star
type: Concept
definition: h alpha emission line star
related: H alpha
related: RW Aurigae star
related: T association
related: variable star

H alpha photometry
type: Concept
broader: narrow band photometry
definition: h alpha photometry
related: H alpha

H and K line
type: Concept
broader: calcium line
definition: H and K line
narrower: H line
narrower: K line

Hanle effect
type: Concept
definition: Hanle effect
related: Sun
related: prominence

Harman-Seaton sequence
type: Concept
alternative label: Harman Seaton sequence
definition: Harman-Seaton sequence
related: Hertzsprung-Russell diagram
related: planetary nebula
related: subdwarf

harmonic frequency
type: Concept
alternative label: harmonic overtones
alternative label: harmonics
definition: harmonic frequency
related: Fourier analysis
related: Fourier component
related: fundamental frequency
related: overtone frequency
scope note: refers only to Fourier component of non-sinusoidal wave; see also overtone frequency

Haro galaxy
type: Concept
broader: galaxy
definition: Haro galaxy
related: emission line galaxy

Hartmann test
type: Concept
definition: Hartmann test
related: figuring
related: image
related: optical instrument

hassium
type: Concept
alternative label: Hs
broader: fundamental chemical element
definition: hassium (atomic number 108)
history note: FVH: new (2007-OCT-25)

Hawking radiation
type: Concept
definition: Hawking radiation
related: black hole
related: event horizon

Hayashi track
type: Concept
broader: evolutionary track
definition: Hayashi track
related: Hertzsprung-Russell diagram
related: convection

H beta
type: Concept
broader: Balmer series
definition: H beta (486 nm)
related: H beta photometry

H beta photometry
type: Concept
broader: narrow band photometry
definition: h beta photometry
related: H beta
related: Stromgren photometry

HD curve
type: Concept
definition: HD curve
related: photography
scope note: Hurter and Driffield curve

H delta
type: Concept
broader: Balmer series
definition: H delta (410 nm)

head tail galaxy
type: Concept
broader: galaxy
broader: radio galaxy
broader: radio source
definition: head tail galaxy
related: radio structure
related: tail

heat-transfer
type: Concept
broader: energy-transfer
definition: heat transfer

heavy element
type: Concept
broader: chemical element
definition: heavy element
related: abundance

heavy metal star
type: Concept
broader: late-type giant
broader: peculiar star
definition: heavy metal star
related: S star
related: barium star
related: zirconium star

He I
type: Concept
broader: helium
broader: neutral gas
definition: neutral helium

height
type: Concept
alternative label: elevation
definition: altitude [height]
scope note: use altitude [angle] for angle

He II
type: Concept
broader: helium
definition: once-ionized helium

He III
type: Concept
broader: helium
definition: twice-ionized helium

He II ionization zone
type: Concept
alternative label: He+ ionisation zone UK
alternative label: He+ ionization zone
change note: FVH: replaced + with II for better parsing of token (2007-OCT-12)
definition: He II ionization zone
related: Cepheid
related: ZZ Ceti star
related: delta Scuti star
related: kappa mechanism
related: pulsating variable star
related: pulsation theory
related: radial pulsation
related: variable star

heliocentric correction
type: Concept
definition: heliocentric correction
related: Astronomical Unit
related: coordinate system
related: heliocentric Julian Date
related: heliocentric velocity
scope note: correction of velocity and times to the Sun's position

heliocentric Julian Date
type: Concept
alternative label: H.J.D.
alternative label: HJD
broader: Julian Date
definition: heliocentric Julian Date
related: heliocentric correction

heliocentric orbit
type: Concept
broader: orbit
definition: heliocentric orbit

heliocentric velocity
type: Concept
broader: velocity
definition: heliocentric velocity
related: heliocentric correction

heliograph
type: Concept
definition: heliograph

heliometer
type: Concept
broader: measuring instrument
definition: heliometer

heliopause
type: Concept
definition: heliopause
related: solar atmosphere
related: solar wind

helioseismology
type: Concept
alternative label: solar seismology
broader: asteroseismology
broader: seismology
definition: helioseismology
related: solar oscillation

heliosphere
type: Concept
definition: heliosphere
related: interplanetary matter
related: interstellar gas
related: solar activity
related: solar atmosphere
related: solar wind

heliostat
type: Concept
broader: coelostat
definition: heliostat
related: siderostat
related: solar telescope
related: telescope mounting

helium burning
type: Concept
broader: nuclear fusion
broader: nucleosynthesis
definition: helium burning
related: carbon burning
related: helium flash
related: helium shell flash
related: hydrogen burning
related: inner core
related: oxygen burning
related: shell burning
related: silicon burning
related: stellar evolution
related: stellar interior

helium flash
type: Concept
alternative label: helium detonation
definition: helium flash
related: carbon flash
related: helium burning
related: helium shell flash
related: nuclear fusion
related: red giant tip

helium
type: Concept
alternative label: He
broader: fundamental chemical element
definition: helium (atomic number 2)
history note: FVH: new (2007-OCT-25)
narrower: He I
narrower: He II
narrower: He III

helium-poor star
type: Concept
alternative label: helium poor star
broader: star
definition: helium-poor star
narrower: Bw star
related: abundance
related: metal abundance

helium-rich star
type: Concept
alternative label: helium rich star
broader: star
change note: FVH: added NT DB_STARS (2007-OCT-1)
definition: helium-rich star
narrower: DB star
related: abundance
related: metal abundance

helium shell flash
type: Concept
definition: helium shell flash
related: helium burning
related: helium flash
related: nuclear fusion

Helmholtz-Kelvin contraction
type: Concept
alternative label: Helmholtz Kelvin contraction
alternative label: Kelvin-Helmholtz contraction
definition: Helmholtz-Kelvin contraction
related: Kelvin timescale

Henry Draper catalog
type: Concept
broader: catalog
definition: henry draper catalog
related: Henry Draper system
related: spectral classification

Henry Draper system
type: Concept
alternative label: HD system
alternative label: Harvard classification
broader: spectral classification
definition: Henry-Draper system
related: Henry Draper catalog

Henyey track
type: Concept
broader: evolutionary track
definition: Henyey track
related: Hertzsprung-Russell diagram
related: stellar evolution

H epsilon
type: Concept
broader: Balmer series
definition: H epsilon

Herbig AeBe star
type: Concept
alternative label: Herbig Ae-Be star
alternative label: Herbig star
broader: Ae star
broader: Be star
definition: Herbig AeBe star
narrower: Ae star
narrower: Be star

Herbig-Haro object
type: Concept
alternative label: HH-object
broader: emission line object
broader: emission nebula
broader: infrared source
broader: intrinsic variable star
broader: pre-main sequence star
definition: Herbig-Haro object
related: T association
related: T Tauri star
related: protostar

Hertzsprung gap
type: Concept
definition: Hertzsprung gap
related: Hertzsprung-Russell diagram
related: giant branch

Hertzsprung-Russell diagram
type: Concept
alternative label: HR diagram
alternative label: Hertzsprung Russell diagram
definition: Hertzsprung-Russell diagram
related: Harman-Seaton sequence
related: Hayashi track
related: Henyey track
related: Hertzsprung gap
related: Hess diagram
related: absolute magnitude
related: asymptotic giant branch
related: color-luminosity relation
related: color-magnitude relation
related: evolutionary track
related: giant branch
related: instability strip
related: luminosity
related: main sequence
related: post-asymptotic giant branch
related: red giant tip
related: spectrum
related: stellar evolution
related: turnoff point
related: zero-age horizontal branch
related: zero-age main sequence

Hess diagram
type: Concept
definition: Hess diagram
related: Hertzsprung-Russell diagram
related: frequency distribution

heterodyne
type: Concept
definition: heterodyne
related: interferometer
related: spectroscopy
scope note: combine with other terms

H gamma
type: Concept
broader: Balmer series
definition: H gamma (434 nm)

H I
type: Concept
alternative label: neutral hydrogen
broader: hydrogen
broader: neutral gas
definition: H I
related: 21-cm line
related: H I absorption
related: H I cloud
related: H I content
related: H I emission
related: H I region

H I absorption
type: Concept
definition: H I absorption
related: 21-cm line
related: H I
related: H I cloud

Hickson compact group
type: Concept
alternative label: HCG
broader: galaxy group
definition: Hickson compact group of galaxies
history note: FVH: new (2007-OCT-8)

H I cloud
type: Concept
definition: H I cloud
related: 21-cm line
related: H I
related: H I absorption

H I content
type: Concept
definition: H I content
related: 21-cm line
related: H I

H I emission
type: Concept
definition: H I emission
related: 21-cm line
related: H I
related: emission spectrum

hierarchical cosmology
type: Concept
broader: cosmology
definition: hierarchical cosmology

high-energy astrophysics
type: Concept
alternative label: high energy astrophysics
alternative label: high energy process
alternative label: high-energy process
broader: astrophysics
definition: high-energy astrophysics
related: cosmic ray astronomy
related: inverse Compton effect
related: nuclear astrophysics
related: particle beam

high-energy radiation
type: Concept
alternative label: high energy radiation
broader: radiation
definition: high-energy radiation
narrower: X-ray radiation
narrower: cosmic ray
narrower: gamma-ray radiation
related: X-ray luminosity

high-luminosity star
type: Concept
alternative label: high luminosity star
alternative label: luminous star
broader: star
definition: high-luminosity star
narrower: bright star
narrower: luminous blue variable star
narrower: nova
narrower: supergiant
narrower: supernova

high-mass star
type: Concept
broader: star
definition: high-mass star
history note: FVH: new (2007-OCT-9)
narrower: high-mass X-ray binary star

high-mass X-ray binary star
type: Concept
broader: X-ray binary star
broader: high-mass star
definition: high-mass X-ray binary star
history note: ES: new (2007-OCT-8)
related: low-mass X-ray binary star

high-resolution spectrosopy
type: Concept
alternative label: high dispersion spectroscopy
alternative label: high resolution spectrosopy
alternative label: high-dispersion spectroscopy
broader: spectroscopy
definition: high-resolution spectrosopy
related: Coude spectrograph
related: echelle spectrograph

high-resolution spectrum
type: Concept
alternative label: high dispersion spectrum
alternative label: high resolution spectrum
alternative label: high-dispersion spectrum
definition: high-resolution spectrum
narrower: Coude spectrum
narrower: echelle spectrum
related: Coude spectrograph
related: echelle spectrograph

high-speed photometer
type: Concept
alternative label: high speed photometer
broader: photometer
definition: high-speed photometer
related: time-resolved spectroscopy
related: variable star

high-state
type: Concept
definition: photometric high state of variable object
history note: FVH: new (2007-OCT-8)
related: low-state
related: outburst
related: variability
related: variable source

high-temperature
type: Concept
alternative label: high temperature
alternative label: hot
definition: high-temperature
scope note: combine with other terms

high-velocity cloud
type: Concept
alternative label: HVC
alternative label: high velocity cloud
broader: cloud
change note: FVH: added ALT HVC (2007-SEP-21)
definition: high-velocity cloud
related: Galactic rotation
related: Milky Way galaxy
related: high-velocity star
related: velocity

high-velocity star
type: Concept
alternative label: high velocity star
broader: star
definition: high-velocity star
related: Galactic rotation
related: Milky Way galaxy
related: high-velocity cloud
related: orbit
related: runaway star
related: velocity

H II
type: Concept
alternative label: ionized hydrogen
broader: hydrogen
broader: ionized gas
definition: H II
related: H II region

H II region
type: Concept
alternative label: HII region
broader: emission line object
broader: emission nebula
broader: interstellar matter
definition: H II region
narrower: compact H II region
related: Bok globule
related: Faraday effect
related: H II
related: cometary globule
related: emission line
related: emission line galaxy
related: exciting star
related: plasma
related: radio recombination line
related: young star

Hirayama family
type: Concept
broader: minor planet family
definition: Hirayama family
related: Apollo group

H I region
type: Concept
broader: interstellar matter
definition: H I region
related: 21-cm line
related: H I
related: neutral gas
related: radio absorption
related: radio recombination line

history of astronomy
type: Concept
definition: history of astronomy
narrower: archaeoastronomy
scope note: combine with other terms

H line
type: Concept
broader: Fraunhofer line
broader: H and K line
definition: H line
related: K line

H magnitude
type: Concept
broader: apparent magnitude
definition: H magnitude
related: infrared photometry
related: near infrared radiation

Holmberg radius
type: Concept
definition: Holmberg radius
related: galaxy

holmium
type: Concept
alternative label: Ho
broader: fundamental chemical element
broader: rare earth
definition: holmium (atomic number 67)
history note: FVH: new (2007-OCT-25)
related: holmium star

holmium star
type: Concept
broader: Ap star
broader: peculiar star
definition: holmium star
related: holmium

Holtsmark approximation
type: Concept
definition: Holtsmark approximation
related: plasma

horizon coordinate system
type: Concept
broader: coordinate system
definition: horizon coordinate system
related: altazimuth mounting
related: altitude angle
related: azimuth
related: horizon
related: meridian
related: nadir
related: zenith

horizon
type: Concept
definition: horizon
related: altitude angle
related: azimuth
related: celestial sphere
related: horizon coordinate system

horizontal branch star
type: Concept
broader: evolved star
broader: population II star
definition: horizontal branch star
narrower: extreme horizontal branch star
related: RR Lyrae star
related: giant branch star
related: globular star cluster

horizontal parallax
type: Concept
broader: diurnal parallax
definition: horizontal parallax

horn antenna
type: Concept
alternative label: horn antennas
broader: antenna
broader: radio waveguide
definition: horn antenna
related: feed horn

horseshoe mounting
type: Concept
broader: equatorial mounting
definition: horseshoe mounting

hour angle
type: Concept
alternative label: HA
definition: hour angle
related: Right Ascension
related: sidereal time
related: transit time

HST photometry
type: Concept
alternative label: HST Fnnn[LMNW] photometry
alternative label: Hubble photometry
broader: broad band photometry
broader: photometric system
definition: HST photometry
history note: FVH: new (2007-SEP-21)
related: Hubble Space Telescope

Hubble classification
type: Concept
alternative label: Hubble sequence
definition: Hubble classification
related: galaxy

Hubble constant
type: Concept
broader: cosmological parameter
definition: Hubble constant
related: Hubble time
related: cosmological distance scale
related: cosmology
related: redshift magnitude relation

Hubble diagram
type: Concept
broader: statistical relation
definition: Hubble diagram
related: cosmology
related: galaxy
related: redshift
related: redshift magnitude relation

Hubble law
type: Concept
broader: statistical relation
definition: Hubble law
related: Dark Energy
related: cosmology
related: observational cosmology
related: redshift
related: redshift magnitude relation

Hubble radius
type: Concept
definition: Hubble radius
related: Big Bang theory
related: cosmology

Hubble Sandage variable star
type: Concept
alternative label: H S variable star
alternative label: H-S variable star
definition: Hubble-Sandage variable star
related: supergiant

Hubble Space Telescope
type: Concept
alternative label: HST
broader: optical observatory
broader: space observatory
broader: ultraviolet observatory
definition: Hubble Space Telescope
history note: FVH: new, because of HST_photometry (2007-NOV-1)
related: HST photometry

Hubble time
type: Concept
definition: Hubble time
related: Big Bang theory
related: Hubble constant
related: age
related: cosmology

hydrated carbon
type: Concept
alternative label: CH
broader: carbon compound
broader: hydrocarbon
broader: interstellar molecule
broader: molecule
change note: FVH: moved CH to ALT to conform to standard use in the thesaurus (2007-OCT-5)
definition: CH molecule

hydrocarbon
type: Concept
definition: hydrocarbon
narrower: CS
narrower: ethane
narrower: ethylene
narrower: hydrated carbon
narrower: polycyclic hydrocarbon

hydrodynamics
type: Concept
broader: fluid dynamics
definition: hydrodynamics
related: jet
related: magnetohydrodynamics

hydrogen burning
type: Concept
broader: nucleosynthesis
definition: hydrogen burning
narrower: carbon nitrogen cycle
narrower: proton-proton reaction
related: Chandrasekhar mass
related: Chandrasekhar-Schoenberg limit
related: carbon burning
related: helium burning
related: hydrogen
related: inner core
related: nuclear fusion
related: oxygen burning
related: shell burning
related: silicon burning
related: stellar evolution
related: stellar interior

hydrogen deficient star
type: Concept
broader: star
definition: hydrogen-deficient star
narrower: AM Canum Venaticorum star
related: hydrogen
related: metal abundance

hydrogen
type: Concept
alternative label: H
broader: fundamental chemical element
definition: hydrogen (atomic number 1)
history note: FVH: new (2007-OCT-25)
narrower: H I
narrower: H II
narrower: deuterium
narrower: molecular hydrogen
narrower: negative H ion
narrower: tritium
related: 21-cm line
related: hydrogen burning
related: hydrogen deficient star
related: hydrogen spectrum

hydrogen line
type: Concept
definition: hydrogen line
scope note: see hydrogen spectrum

hydrogen spectrum
type: Concept
broader: spectrum
definition: hydrogen spectrum
narrower: Balmer continuum
narrower: Balmer series
narrower: Brackett series
narrower: Lyman continuum
narrower: Lyman series
narrower: Paschen series
narrower: Pfund series
related: hydrogen

hydrostatic equilibrium
type: Concept
definition: hydrostatic equilibrium
related: stellar structure

hydroxyl radical
type: Concept
alternative label: OH
alternative label: OH radical
broader: interstellar molecule
broader: ion
broader: radical
definition: hydroxyl radical
related: OH absorption
related: OH cloud
related: OH emission
related: OH IR star
related: OH line
related: OH maser
related: OH source

hyperbolic orbit
type: Concept
broader: orbit
definition: hyperbolic orbit
related: circular orbit
related: elliptical orbit
related: parabolic orbit

hyperfine line
type: Concept
broader: spectral line
definition: hyperfine line
related: spectrum

hypergalaxy
type: Concept
broader: galaxy
definition: hypergalaxy

hypergiant
type: Concept
broader: star
definition: hypergiant star
related: supergiant

hypernova
type: Concept
broader: supernova
definition: hypernova
history note: FVH: new (2007-OCT-5)
related: gamma-ray burst
related: stellar black hole

hypothetical planet
type: Concept
broader: planet
definition: hypothetical planet

HZ Herculis star
type: Concept
broader: X-ray pulsar
broader: low-mass star
broader: neutron star
definition: HZ Herculis star
related: X-ray binary star
related: X-ray burst

identification
type: Concept
definition: identification
scope note: e.g. catalog number, etc

I galaxy
type: Concept
broader: irregular galaxy
definition: irregular galaxy (Yerkes classification scheme)
history note: FVH: new (2007-OCT-12)
related: Yerkes classification

illumination
type: Concept
definition: illumination
related: albedo
related: brightness
related: intensity
related: lunar phase
related: radiation
scope note: of solar system body

image
type: Concept
definition: image
narrower: digital image
narrower: photograph
related: Hartmann test
related: halation
related: photography
related: vision

image processing
type: Concept
definition: image processing
related: clean method
related: flat field
related: image reconstruction
related: two-dimensional detector

image reconstruction
type: Concept
definition: image reconstruction
related: clean method
related: image processing

image tube
type: Concept
alternative label: image converters
alternative label: image intensifier
alternative label: light amplifier
alternative label: photoelectric image tube
broader: multi-channel detector
broader: photoelectric instrument
broader: photoelectronic device
broader: two-dimensional detector
definition: image tube
related: amplifier
related: electrode
related: electronic camera
related: microchannel plate
related: phosphorescence
related: phosphorescent scintillation
related: photocathode
related: quantum efficiency
related: scintillation counter

imaging instrument
type: Concept
broader: instrument
definition: imaging instrument
scope note: combine with other terms

I magnitude
type: Concept
broader: apparent magnitude
definition: I magnitude
related: Bessel photometry
related: Johnson photometry
related: Kron-Cousins photometry
related: infrared photometry
related: near infrared radiation

impact crater
type: Concept
broader: crater
definition: impact crater
related: meteorite

impersonal astrolabe
type: Concept
broader: astrolabe
definition: impersonal astrolabe

inclination
type: Concept
broader: orbital element
definition: inclination
related: binary star
related: node

indium
type: Concept
alternative label: In
broader: fundamental chemical element
definition: indium (atomic number 49)
history note: FVH: new (2007-OCT-25)

indochinite
type: Concept
broader: tektite
definition: indochinite

inertial coordinate system
type: Concept
broader: coordinate system
definition: inertial coordinate system
related: inertial reference frame
related: relativity

inertial reference frame
type: Concept
definition: inertial reference frame
related: inertial coordinate system
related: relativity

inflationary universe
type: Concept
broader: cosmology
definition: inflationary universe

infrared astronomy
type: Concept
broader: astronomy
definition: infrared astronomy
related: infrared radiation
related: infrared telescope
related: satellite-borne instrument

infrared detector
type: Concept
broader: detector
definition: infrared detector
related: photometer

infrared emission
type: Concept
broader: emission spectrum
definition: infrared emission
related: thermal emission

infrared galaxy
type: Concept
broader: galaxy
broader: infrared source
definition: infrared galaxy
narrower: IRAS galaxy

infrared
type: Concept
definition: infrared
related: infrared radiation
scope note: combine with other terms

infrared observatory
type: Concept
broader: observatory
definition: infrared observatory
narrower: IRAS satellite
related: airplane-borne instrument
related: infrared source
related: rocket-borne instrument
related: space observatory
scope note: see observatory for more rts

infrared photometry
type: Concept
broader: broad band photometry
broader: medium band photometry
broader: photometry
definition: infrared photometry
related: H magnitude
related: I magnitude
related: J magnitude
related: K magnitude
related: L magnitude
related: M magnitude
related: N magnitude
related: O magnitude
related: P magnitude
related: Q magnitude
related: far infrared radiation
related: near infrared radiation

infrared radiation
type: Concept
broader: electromagnetic radiation
broader: radiation
definition: infrared radiation
narrower: Brackett series
narrower: Pfund series
narrower: Phillips band
narrower: far infrared radiation
narrower: near infrared radiation
related: IRAS satellite
related: greenhouse effect
related: infrared
related: infrared astronomy
related: remote sensing
related: terrestrial radiation
related: thermal radiation

infrared source
type: Concept
broader: source
definition: infrared source
narrower: FU Orionis star
narrower: Herbig-Haro object
narrower: OH IR star
narrower: cocoon star
narrower: extreme carbon star
narrower: flare star
narrower: infrared galaxy
related: infrared observatory
related: star formation

infrared telescope
type: Concept
broader: telescope
definition: infrared telescope
related: infrared astronomy

infrared transmission window
type: Concept
broader: atmospheric window
change note: FVH: renamed to avoid confusion with optics (2007-NOV-2)
definition: infrared transmission window through the atmosphere
related: optical transmission window
related: radio transmission window
scope note: low absorption in atmosphere

inhomogenity
type: Concept
definition: inhomogenity
scope note: combine with other terms

initial mass function
type: Concept
alternative label: IMF
definition: initial mass function
related: mass
related: mass-ratio
related: star cluster
related: stellar evolution

inner core
type: Concept
definition: inner core
related: helium burning
related: hydrogen burning
related: stellar evolution
related: stellar interior
scope note: central region of star

inner planet
type: Concept
alternative label: terrestrial planet
broader: planet
definition: inner planet
related: outer planet

instability
type: Concept
definition: instability
narrower: Rayleigh-Taylor instability
scope note: combine with other terms

instability strip
type: Concept
definition: instability strip
related: Cepheid
related: Hertzsprung-Russell diagram
related: giant branch
related: stellar evolution

instrumental profile
type: Concept
broader: line profile
definition: instrumental profile
related: equivalent width
related: line broadening
related: line width
related: spectral line

instrument
type: Concept
alternative label: astronomical instrument
alternative label: instrumentation
definition: instrument
narrower: airplane-borne instrument
narrower: amplifier
narrower: armillary sphere
narrower: astrolabe
narrower: astrometric instrument
narrower: auxiliary instrument
narrower: blink comparator
narrower: bolometer
narrower: coronagraph
narrower: detector
narrower: guide system
narrower: imaging instrument
narrower: interferometer
narrower: magnetograph
narrower: magnetoheliograph
narrower: quadrant
narrower: sextant
narrower: spectrograph
narrower: stroboscope
narrower: telescope instrument
related: calibration
related: electronic equipment
related: frequency standard
related: metrology
related: peripheral
related: support system
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

integral field spectrograph
type: Concept
broader: spectrograph
definition: integral field spectrograph
history note: FVH: new (2007-SEP-21)
related: multi-fiber spectrograph
related: multi-slit spectrograph
related: three-dimensional spectrum

integrated magnitude
type: Concept
alternative label: total magnitude
broader: magnitude
definition: integrated magnitude
related: galaxy
related: star cluster

integration time
type: Concept
definition: integration time
related: brightness
related: noise
related: sensitivity
related: signal-to-noise ratio

intensity
type: Concept
alternative label: specific intensity
definition: intensity
narrower: apparent intensity
related: brightness
related: illumination
related: luminosity
related: magnitude
scope note: combine with other terms

intensity interferometer
type: Concept
broader: interferometer
broader: optical interferometer
definition: intensity interferometer
related: Michelson interferometer

interacting binary star
type: Concept
broader: binary star
definition: interacting binary star
narrower: X-ray binary star
narrower: cataclysmic variable star
related: Roche lobe
related: X-ray bright point
related: eclipsing binary star
related: eruptive binary star
related: tidal friction
related: tidal interaction

interacting galaxy
type: Concept
broader: galaxy
broader: peculiar galaxy
definition: interacting galaxy
related: galaxy encounter
related: galaxy merger
related: tail
related: tidal distortion
related: tidal friction
related: tidal interaction

interaction
type: Concept
definition: interaction
narrower: electromagnetic interaction
narrower: gravitational interaction
narrower: strong interaction
narrower: weak interaction
related: equation of state
related: nuclear physics

intercloud gas
type: Concept
broader: intercloud matter
definition: intercloud gas

intercloud matter
type: Concept
broader: interstellar matter
definition: intercloud matter
narrower: intercloud gas

interference filter
type: Concept
broader: filter
broader: optical component
broader: optical filter
definition: interference filter
related: interference wave
related: optical film
related: photometry
related: ultraviolet filter

interference fringe
type: Concept
alternative label: fringe
alternative label: fringe patterns
definition: interference fringe
related: interference wave
related: interferometer
related: interferometry
related: optical interferometry
related: visibility function

interference noise
type: Concept
broader: noise
definition: interference [noise]

interference spectrosocopy
type: Concept
broader: spectroscopy
definition: interference spectrosocopy
related: interference wave

interference wave
type: Concept
definition: interference [wave]
narrower: light interference
related: diffraction
related: interference filter
related: interference fringe
related: interference spectrosocopy
related: interferometry
related: optical interferometry
related: radio interferometry
related: shadow band
related: wave motion

interferometer
type: Concept
broader: instrument
definition: interferometer
narrower: Fabry-Perot interferometer
narrower: intensity interferometer
narrower: long baseline interferometer
narrower: optical interferometer
narrower: phase switching interferometer
narrower: radio interferometer
narrower: very long baseline interferometer
related: antenna
related: array
related: heterodyne
related: interference fringe
related: radio telescope
related: telescope array
scope note: see also under interferometry

interferometric correlation
type: Concept
broader: correlation
change note: FVH: changed from correlation to avoid mixup with generic term (2007-OCT-26)
definition: interferometric correlation
related: cross-correlation
related: interferometry
related: receiver
scope note: combine with other terms

interferometry
type: Concept
broader: astronomical technique
broader: observing technique
definition: interferometry
narrower: long baseline interferometry
narrower: optical interferometry
narrower: radio interferometry
narrower: speckle interferometry
narrower: very long baseline interferometry
related: angular diameter
related: aperture synthesis
related: correlation
related: interference fringe
related: interference wave
related: interferometric correlation
related: radio astrometry
related: resolution
related: visibility function
scope note: see also under interferometer

intergalactic absorption
type: Concept
broader: absorption
definition: intergalactic absorption
related: Lyman alpha forest
related: absorption coefficient
related: intergalactic matter
related: intergalactic space
related: interstellar absorption
related: reddening

intergalactic cloud
type: Concept
broader: intergalactic matter
definition: intergalactic cloud
related: intergalactic gas

intergalactic gas
type: Concept
broader: intergalactic matter
definition: intergalactic gas
related: intergalactic cloud

intergalactic matter
type: Concept
definition: intergalactic matter
narrower: Dark Matter
narrower: dust
narrower: intergalactic cloud
narrower: intergalactic gas
related: cosmic string
related: galaxy cluster
related: intergalactic absorption
related: intergalactic space
related: interplanetary matter
related: interstellar matter
related: intracluster matter

intergalactic space
type: Concept
definition: intergalactic space
related: galaxy void
related: intergalactic absorption
related: intergalactic matter

interior
type: Concept
definition: interior
related: planet
scope note: combine with other terms

intermediate population star
type: Concept
broader: star
definition: intermediate population star
related: population II star
related: stellar population

intermediate type star
type: Concept
definition: intermediate type star
narrower: F star
narrower: G star

internal motion
type: Concept
broader: motion
definition: internal motion
scope note: combine with other terms

interplanetary dust
type: Concept
broader: dust
broader: interplanetary matter
definition: interplanetary dust
narrower: meteoroid
related: grain
related: interplanetary gas

interplanetary gas
type: Concept
broader: interplanetary matter
definition: interplanetary gas
related: interplanetary dust
related: interplanetary grain
related: solar wind

interplanetary grain
type: Concept
broader: grain
broader: interplanetary matter
definition: interplanetary grain
narrower: meteoroid
related: adsorption
related: graphite
related: interplanetary gas

interplanetary magnetic field
type: Concept
broader: magnetic field
definition: interplanetary magnetic field

interplanetary matter
type: Concept
alternative label: interplanetary medium
definition: interplanetary matter
narrower: interplanetary dust
narrower: interplanetary gas
narrower: interplanetary grain
narrower: meteoroid
narrower: solar wind
related: asteroid
related: circumstellar matter
related: comet
related: gegenschein
related: heliosphere
related: intergalactic matter
related: interplanetary scintillation
related: interstellar matter
related: meteorite
related: micrometeorite
related: zodiacal dust
related: zodiacal light

interplanetary scintillation
type: Concept
broader: scintillation
definition: interplanetary scintillation
related: interplanetary matter
related: interstellar scintillation
related: ionospheric scintillation
related: radio source

interstellar absorption
type: Concept
alternative label: interstellar extinction
broader: absorption
definition: interstellar absorption
narrower: OH absorption
related: Galactic window
related: Rayleigh scattering
related: Wolf diagram
related: absorption coefficient
related: intergalactic absorption
related: interstellar dust
related: interstellar gas
related: interstellar reddening
related: light absorption
related: reddened star
related: reddening
related: window

interstellar bubble
type: Concept
broader: bubble
definition: interstellar bubble
scope note: combine with other terms

interstellar communication
type: Concept
definition: interstellar communication
related: extraterrestrial life
related: space exploration

interstellar dust
type: Concept
broader: dust
broader: interstellar matter
definition: interstellar dust
related: adsorption
related: dust cloud
related: grain
related: graphite
related: interstellar absorption
related: interstellar gas
related: reddening

interstellar gas
type: Concept
broader: interstellar matter
definition: interstellar gas
related: absorption
related: heliosphere
related: interstellar absorption
related: interstellar dust
related: interstellar wind
related: reddening

interstellar magnetic field
type: Concept
broader: magnetic field
definition: interstellar magnetic field
related: spiral arm

interstellar matter
type: Concept
alternative label: interstellar medium
definition: interstellar matter
narrower: Bok globule
narrower: C II region
narrower: Dark Matter
narrower: H I region
narrower: H II region
narrower: OH cloud
narrower: cometary globule
narrower: dark cloud
narrower: dark nebula
narrower: dense cloud
narrower: dust
narrower: dust cloud
narrower: dust grain
narrower: dust nebula
narrower: globule
narrower: grain
narrower: intercloud matter
narrower: interstellar dust
narrower: interstellar gas
narrower: interstellar molecule
narrower: molecular cloud
narrower: nebula
narrower: nebular filament
narrower: reflection nebula
related: SiO maser
related: Stromgren sphere
related: circumstellar matter
related: cosmic string
related: galaxy structure
related: intergalactic matter
related: interplanetary matter
related: interstellar reddening
related: interstellar scintillation
related: maser
related: radio absorption
related: radio transmission window
related: selective absorption
related: spiral arm
related: torus

interstellar molecule
type: Concept
broader: interstellar matter
broader: molecule
definition: interstellar molecule
narrower: CS
narrower: ammonia
narrower: carbon compound
narrower: hydrated carbon
narrower: hydroxyl radical
narrower: methane
narrower: molecular hydrogen
narrower: water
related: cosmochemistry
related: giant molecular cloud
related: molecular cloud
related: organic molecule
scope note: not a complete list of nts

interstellar reddening
type: Concept
broader: reddening
definition: interstellar reddening
related: color excess
related: gas to dust ratio
related: interstellar absorption
related: interstellar matter
related: light absorption
related: light scattering
related: reddened star
related: reddening law
related: selective absorption

interstellar scintillation
type: Concept
broader: scintillation
definition: interstellar scintillation
related: interplanetary scintillation
related: interstellar matter
related: ionospheric scintillation
related: radio source

interstellar wind
type: Concept
definition: interstellar wind
related: interstellar gas
related: solar wind
related: stellar wind

intracluster matter
type: Concept
definition: intracluster matter
related: Sunyaev-Zeldovich effect
related: galaxy cluster
related: intergalactic matter

intrinsic color
type: Concept
definition: intrinsic color
related: color index
related: photometry
related: reddening

intrinsic variable star
type: Concept
alternative label: unstable star
broader: variable star
definition: intrinsic variable star
narrower: Herbig-Haro object
narrower: magnetic variable star
narrower: pulsating variable star
narrower: spectrum variable star

inverse Compton effect
type: Concept
definition: inverse Compton effect
related: cosmic ray
related: electron
related: high-energy astrophysics
related: photon

inverse Compton scattering
type: Concept
definition: inverse Compton scattering
related: Compton scattering
related: electron
related: photon

inverse maser
type: Concept
definition: inverse maser
related: maser

iodine cell
type: Concept
broader: optical filter
broader: radial velocity
definition: iodine cell
history note: FVH: new (2007-OCT-25)

iodine
type: Concept
alternative label: I
broader: fundamental chemical element
definition: iodine (atomic number 53)
history note: FVH: new (2007-OCT-25)

ion composition
type: Concept
definition: ion composition
related: ion

ion density
type: Concept
definition: ion density
related: ion
related: ionization

ion
type: Concept
alternative label: charged particle
broader: composite particle
broader: particle
definition: ion
narrower: hydroxyl radical
related: Paul trap
related: Saha equation
related: collisional excitation
related: collisional plasma
related: ion composition
related: ion density
related: ion plasma wave
related: ionized gas
related: plasma
related: plasma cloud
related: plasma jet
related: polarization charge separation
related: radical
related: thermionic emission

ionization equilibrium
type: Concept
alternative label: ionisation equilibrium UK
definition: ionization equilibrium
related: ionization

ionization
type: Concept
alternative label: ionisation UK
definition: ionization
narrower: photoionization
related: Schwarzschild metric
related: Stromgren sphere
related: corona
related: ion density
related: ionization equilibrium
related: shock

ionized gas
type: Concept
broader: gas
definition: ionized gas
narrower: H II
related: Stromgren sphere
related: collisional excitation
related: ion
related: plasma

ionizing shock wave
type: Concept
broader: shock wave
definition: ionizing shock wave

ionosphere
type: Concept
definition: ionosphere
related: D layer
related: E layer
related: Earth atmosphere
related: F layer
related: exosphere
related: ionospheric scintillation
related: mesopause
related: radio absorption
related: thermosphere
related: upper atmosphere

ionospheric scintillation
type: Concept
broader: scintillation
definition: ionospheric scintillation
related: interplanetary scintillation
related: interstellar scintillation
related: ionosphere
related: radio source

ion plasma wave
type: Concept
definition: ion plasma wave
related: ion
related: plasma wave

ion temperature
type: Concept
broader: temperature
definition: ion temperature

IRAS galaxy
type: Concept
broader: infrared galaxy
definition: IRAS galaxy
related: IRAS satellite

IRAS satellite
type: Concept
alternative label: IRAS
broader: infrared observatory
broader: space observatory
definition: InfraRed Astronomical Satellite
history note: FVH: new, because of IRAS_galaxy (2007-NOV-1)
related: IRAS galaxy
related: infrared radiation

iridium
type: Concept
alternative label: Ir
broader: fundamental chemical element
definition: iridium (atomic number 77)
history note: FVH: new (2007-OCT-25)

iron
type: Concept
alternative label: Fe
broader: fundamental chemical element
definition: iron (atomic number 26)
history note: FVH: new (2007-OCT-25)
related: iron meteorite

iron meteorite
type: Concept
broader: meteorite
definition: iron meteorite
related: iron

irradiance
type: Concept
definition: irradiance
related: radiation

irregular galaxy
type: Concept
broader: galaxy
definition: irregular galaxy
narrower: I galaxy
narrower: Magellanic cloud

irregular variable star
type: Concept
broader: late-type giant
broader: pulsating variable star
broader: variable star
definition: irregular variable star
narrower: Mira variable star
narrower: R Coronae Borealis star
narrower: RV Tauri star
narrower: RW Aurigae star
narrower: T Tauri star
narrower: UU Herculis star
narrower: dwarf Cepheid
narrower: gamma Cassiopeiae star
narrower: soft gamma-ray repeater
related: T association
related: late-type supergiant
related: semi-regular variable star
related: supergiant

isophotal diameter
type: Concept
broader: angular diameter
broader: diameter
definition: isophotal diameter
history note: ES: new (2007-OCT-11)
related: galaxy
related: isophot
related: luminosity distribution
related: surface photometry

isophot
type: Concept
definition: isophot
related: contour map
related: isophotal diameter
related: luminosity distribution
related: surface photometry

isothermal sphere
type: Concept
broader: mass distribution
definition: isothermal mass-profile
history note: FVH: new (2007-OCT-5)
related: Burkert profile
related: Navarro-Frenk-White profile
related: exponential profile

isotope
type: Concept
broader: chemical element
definition: isotope
related: deuterium
related: tritium

isotopic abundance
type: Concept
broader: abundance
definition: isotopic abundance
related: isotopic composition

isotopic composition
type: Concept
definition: isotopic composition
related: isotopic abundance

isotropy
type: Concept
definition: isotropy
related: anisotropy
related: optical property

Jansky
type: Concept
definition: Jansky
related: radio radiation
scope note: radio flux density unit

Jeans length
type: Concept
definition: Jeans length
related: Jeans mass
related: gravity
related: star formation

Jeans mass
type: Concept
definition: Jeans mass
related: Jeans length

jet
type: Concept
alternative label: astrophysical jet
broader: mass-loss
definition: jet
narrower: plasma jet
narrower: radio jet
related: comet
related: hydrodynamics
related: radio source

J magnitude
type: Concept
broader: apparent magnitude
definition: J magnitude
related: infrared photometry
related: near infrared radiation

Johnson noise
type: Concept
definition: Johnson noise
related: thermal radiation

Johnson photometry
type: Concept
alternative label: Johnson-Morgan filter system
alternative label: UBV photometry
alternative label: UBVRI photometry
alternative label: UBVRIJKL photometry
alternative label: three-color photometry
broader: broad band photometry
broader: photometric system
definition: Johnson photometry
related: B magnitude
related: Bessel photometry
related: BV photometry
related: Cape photometry
related: Cape RI photometry
related: I magnitude
related: Kron-Cousins photometry
related: R magnitude
related: U magnitude
related: V magnitude
related: e region
related: f region
related: two-color photometry

Jovian planet
type: Concept
broader: outer planet
definition: Jovian planet
narrower: Jupiter
narrower: Neptune
narrower: Saturn
narrower: Uranus

Julian calendar
type: Concept
broader: calendar
definition: Julian calendar
related: Gregorian calendar
related: Julian Date
related: Julian epoch

Julian Date
type: Concept
alternative label: J.D.
alternative label: JD
definition: Julian Date
narrower: heliocentric Julian Date
related: Julian calendar
related: epoch
related: time

Julian epoch
type: Concept
broader: epoch
broader: standard epoch
definition: Julian epoch
related: Besselian epoch
related: Julian calendar
related: time

jump condition
type: Concept
definition: jump condition
related: shock wave

Jupiter
type: Concept
broader: Jovian planet
broader: planet
definition: Jupiter
history note: FVH: new (2007-SEP-24)
related: Solar System

kappa mechanism
type: Concept
definition: kappa mechanism
related: Cepheid
related: He II ionization zone
related: ZZ Ceti star
related: delta Scuti star
related: pulsating variable star

Kapteyn selected area
type: Concept
definition: Kapteyn selected area
narrower: e region
narrower: f region
related: Cape photometry
related: Stromgren photometry

K corona
type: Concept
alternative label: K-corona
broader: corona
definition: K corona
related: solar corona

k correction
type: Concept
alternative label: k-term
definition: k-correction
related: redshift

K dwarf
type: Concept
broader: K star
broader: dwarf
broader: late-type dwarf
definition: K dwarf star
related: K subdwarf

Kellner eyepiece
type: Concept
broader: eyepiece
definition: Kellner eyepiece

Kelvin
type: Concept
broader: absolute temperature scale
definition: Kelvin
related: celsius temperature scale
related: temperature scale
scope note: ES: moved absolute_temperature_scale from RT to BT (2007-OCT-8)
scope note: absolute temperature scale units

Kelvin timescale
type: Concept
definition: Kelvin timescale
related: Helmholtz-Kelvin contraction

Keplerian orbit
type: Concept
broader: orbit
definition: Keplerian orbit
related: celestial mechanics

Kerr black hole
type: Concept
broader: black hole
definition: Kerr black hole
related: stellar evolution

K giant
type: Concept
broader: K star
broader: late-type giant
definition: K giant star
related: K subgiant

kinematic parallax
type: Concept
broader: parallax
definition: kinematic parallax
related: dynamical parallax
related: moving cluster parallax

kinematics
type: Concept
definition: kinematics
narrower: acceleration
related: Galactic rotation
related: Galactic structure
related: angular momentum
related: galaxy rotation curve
related: galaxy structure
related: proper motion
related: radial velocity
related: velocity

kinetic energy
type: Concept
broader: energy
definition: kinetic energy
related: potential energy

Kirkwood gap
type: Concept
broader: resonance gap
definition: Kirkwood gap
related: asteroid

K line
type: Concept
broader: Fraunhofer line
broader: H and K line
broader: calcium line
definition: K line
related: H line
related: Wilson-Bappu effect

K magnitude
type: Concept
broader: apparent magnitude
definition: K magnitude
related: infrared photometry
related: near infrared radiation

Kramers opacity
type: Concept
broader: opacity
definition: Kramers opacity
related: Rosseland opacity

Kreutz sungrazer
type: Concept
alternative label: sungrazer
broader: comet
definition: Kreutz sungrazer
related: Solar System

Kron-Cousins photometry
type: Concept
alternative label: Kron Cousins photometry
alternative label: Kron-Cousins R,I photometry
broader: broad band photometry
broader: photometric system
definition: Kron-Cousins photometry
history note: FVH: new (2007-SEP-21)
related: I magnitude
related: Johnson photometry
related: R magnitude

Kruskal diagram
type: Concept
definition: Kruskal diagram
related: black hole

krypton
type: Concept
alternative label: Kr
broader: fundamental chemical element
definition: krypton (atomic number 36)
history note: FVH: new (2007-OCT-25)

K star
type: Concept
broader: late-type star
definition: K star
narrower: K dwarf
narrower: K giant
narrower: K subdwarf
narrower: K subgiant
narrower: K supergiant
related: spectral type

K subdwarf
type: Concept
broader: K star
broader: subdwarf
definition: K subdwarf star
related: K dwarf

K subgiant
type: Concept
broader: K star
broader: subgiant
definition: K subgiant star
related: K giant

K supergiant
type: Concept
broader: K star
broader: late-type supergiant
broader: supergiant
definition: K supergiant star

Lagrangian point
type: Concept
alternative label: libration point
definition: Lagrangian point
related: celestial mechanics
related: gravitation
related: gravitational field

lambda eridani star
type: Concept
broader: Be star
broader: pulsating variable star
definition: lambda Eridani star

lamp
type: Concept
definition: lamp
narrower: comparison lamp
narrower: flat field lamp
related: calibration
related: electromagnetic radiation

lanthanum
type: Concept
alternative label: La
broader: fundamental chemical element
broader: rare earth
definition: lanthanum (atomic number 57)
history note: FVH: new (2007-OCT-25)

Large Magellanic Cloud
type: Concept
alternative label: LMC
broader: Magellanic cloud
definition: Large Magellanic Cloud
related: Small Magellanic Cloud

large scale structure
type: Concept
change note: FVH: added RT COSMOLOGY (2007-SEP-21)
definition: large scale structure
related: cosmic string
related: cosmology
related: universe

laser
type: Concept
definition: laser
related: coherence
related: electron pumping
related: light coherence
related: lunar laser ranging
related: maser
related: optical radar
related: population inversion
related: satellite laser ranging
related: stimulated emission

laser ranging
type: Concept
definition: laser ranging
narrower: lunar laser ranging
narrower: satellite laser ranging
related: optical radar

late-type dwarf
type: Concept
alternative label: cool dwarf star
alternative label: late type dwarf star
broader: dwarf
broader: late-type star
broader: low-luminosity star
definition: late-type dwarf star
narrower: K dwarf
narrower: L dwarf
narrower: M dwarf
narrower: brown dwarf
narrower: red dwarf flare star

late-type galaxy
type: Concept
alternative label: late type galaxy
broader: galaxy
definition: late-type galaxy
related: spiral galaxy

late-type giant
type: Concept
alternative label: cool giant star
alternative label: late type giant star
broader: giant
broader: late-type star
definition: late-type giant star
narrower: K giant
narrower: M giant
narrower: Mira variable star
narrower: carbon star
narrower: heavy metal star
narrower: irregular variable star
narrower: semi-regular variable star
related: asymptotic giant branch
related: funneling
related: post-asymptotic giant branch
related: red giant tip

late-type star
type: Concept
alternative label: cool star
alternative label: late type star
broader: star
definition: late-type star
narrower: K star
narrower: M star
narrower: N star
narrower: R star
narrower: S star
narrower: late-type dwarf
narrower: late-type giant
narrower: late-type subdwarf
narrower: late-type supergiant
related: Wilson-Bappu effect
related: molecular band
related: molecular line
related: molecular spectrum

late-type subdwarf
type: Concept
alternative label: cool subdwarf star
broader: late-type star
broader: low-luminosity star
broader: subdwarf
definition: late-type subdwarf
narrower: L subdwarf
narrower: brown dwarf

late-type supergiant
type: Concept
alternative label: cool supergiant star
broader: late-type star
broader: supergiant
definition: late-type supergiant star
narrower: K supergiant
narrower: M supergiant
narrower: RV Tauri star
related: irregular variable star
related: long period variable star

late-type variable star
type: Concept
definition: late-type variable star
narrower: Me variable star
related: Me star

latitude determination
type: Concept
definition: latitude determination
narrower: latitude variation
related: Chandler wobble
related: astrometry
scope note: on Earth surface

latitude
type: Concept
definition: latitude
narrower: Declination
narrower: Galactic latitude
narrower: ecliptic latitude
narrower: supergalactic latitude
scope note: on celestial sphere

latitude variation
type: Concept
broader: latitude determination
definition: latitude variation
related: Chandler wobble
related: polar motion
scope note: on Earth surface

lawrencium
type: Concept
alternative label: Lr
broader: fundamental chemical element
definition: lawrencium (atomic number 103)
history note: FVH: new (2007-OCT-25)

Lb variable star
type: Concept
broader: giant
definition: Lb variable star

Lc variable star
type: Concept
definition: Lc variable star
related: supergiant

L dwarf
type: Concept
broader: brown dwarf
broader: late-type dwarf
definition: L dwarf
history note: FVH: new (2007-OCT-2)
related: L subdwarf
related: spectral type
related: titanium oxide

lead
type: Concept
alternative label: Pb
broader: fundamental chemical element
definition: lead (atomic number 82)
history note: FVH: new (2007-OCT-25)

Lemaitre universe
type: Concept
broader: cosmology
definition: Lemaitre universe
related: Big Bang theory

lens antenna
type: Concept
alternative label: lens antennas
broader: antenna
definition: lens antenna

lens design
type: Concept
definition: lens design
related: lens

lens
type: Concept
broader: optical component
definition: lens
narrower: camera lens
narrower: corrector plate
narrower: field corrector
narrower: primary lens
related: antireflection coating
related: catadioptric system
related: coating
related: collimator
related: dioptric system
related: eyepiece
related: figuring
related: glass
related: lens design
related: optical aberration
related: optical instrument
related: optical material
related: optical surface
related: polishing
related: refraction
related: refractive index

lenticular galaxy
type: Concept
alternative label: S0 galaxy
broader: disk galaxy
broader: galaxy
definition: lenticular galaxy
related: ansa

lepton
type: Concept
broader: elementary particle
broader: particle
definition: lepton
narrower: electron
narrower: muon
narrower: neutrino
narrower: positron
related: boson
related: quark

L galaxy
type: Concept
broader: galaxy
definition: low surface-brightness galaxy (Yerkes classification scheme)
related: Yerkes classification
related: surface brightness

libration
type: Concept
alternative label: physical libration
definition: libration
related: Moon

life
type: Concept
definition: life
narrower: extraterrestrial life
related: anthropic principle
related: origin

light absorption
type: Concept
broader: absorption
definition: light absorption
related: atmospheric extinction
related: electromagnetic radiation
related: interstellar absorption
related: interstellar reddening
related: light scattering
related: visible radiation

light coherence
type: Concept
broader: coherence
definition: light coherence
related: laser

light cone
type: Concept
definition: light cone
narrower: future light cone
narrower: past light cone
related: velocity of light

light curve
type: Concept
broader: photometric element
definition: light curve
related: magnitude
related: maximum
related: minimum
related: period
related: phase shift
related: phase wave
related: variable star
related: velocity curve

light emission
type: Concept
definition: light emission
narrower: photoluminescence
related: aurora
related: chemiluminescence
related: continuous spectrum
related: emission spectrum
related: luminescence

light interference
type: Concept
broader: interference wave
definition: light interference
related: electromagnetic radiation
related: optical film
related: optical filter
related: optical interferometry
related: visible radiation

light polarization
type: Concept
alternative label: polarization wave
definition: light polarization
narrower: X-ray polarization
narrower: circular polarization
narrower: plane polarization
related: Faraday effect
related: electromagnetic radiation
related: optical property
related: polarimetry
related: polarized light
related: polarized radiation
related: radiation scattering
related: stokes parameter

light pollution
type: Concept
broader: pollution
definition: light pollution
related: air pollution
related: site protection

light scattering
type: Concept
broader: radiation scattering
broader: scattering
definition: light scattering
narrower: Compton scattering
narrower: Rayleigh scattering
narrower: Thomson scattering
related: Raman spectrum
related: afterglow
related: atmospheric extinction
related: brillouin spectrum
related: electromagnetic radiation
related: halo
related: interstellar reddening
related: light absorption
related: luminescence
related: visible radiation
related: zodiacal light

light year
type: Concept
definition: light year
related: distance
related: parsec
related: velocity of light
related: year

limb brightening
type: Concept
definition: limb brightening
related: atmosphere
related: limb darkening
related: stellar atmosphere
related: temperature

limb darkening
type: Concept
definition: limb darkening
related: atmosphere
related: limb brightening
related: solar atmosphere
related: stellar atmosphere
related: temperature

limiting magnitude
type: Concept
definition: limiting magnitude
related: detector
related: precision
related: sensitivity
related: signal detection
related: signal-to-noise ratio

linearity calibration
type: Concept
broader: calibration
definition: linearity calibration
history note: FVH: new (2007-OCT-3)

line blanketing
type: Concept
definition: line blanketing
related: metal line
related: spectral line
related: ultraviolet radiation

line blending
type: Concept
definition: line blending
related: spectral line
related: spectral resolution

line blocking
type: Concept
definition: line blocking
scope note: see under line blanketing

line broadening
type: Concept
alternative label: spectral line broadening
definition: line broadening
narrower: Doppler broadening
narrower: Stark broadening
narrower: collision broadening
narrower: natural line broadening
narrower: pressure broadening
related: Zeeman splitting
related: convection
related: equivalent width
related: instrumental profile
related: line formation
related: line width
related: natural line width
related: spectral line
related: stellar atmosphere
related: turbulence star atmosphere

line formation
type: Concept
alternative label: spectral line formation
definition: line formation
related: absorption line
related: damping constant
related: emission line
related: g value
related: gf value
related: line broadening
related: oscillator strength
related: solar atmosphere
related: spectral line
related: stellar atmosphere
related: transition probability

line identification
type: Concept
definition: line identification
related: absorption line
related: emission line
related: spectral line

line intensitite
type: Concept
definition: line intensitite
related: emission line
related: spectral line

line of sight
type: Concept
broader: location
definition: line-of-sight
history note: FVH: new (2007-SEP-21)
related: location behind
related: location between
related: location in front

line profile
type: Concept
broader: profile
definition: line profile
narrower: P Cygni line profile
narrower: instrumental profile
related: absorption line
related: emission line
related: residual intensity
related: spectral line

line ratio
type: Concept
definition: line ratio
related: absorption line
related: emission line
related: spectral line

liner galaxy
type: Concept
broader: emission line galaxy
definition: liner galaxy
history note: FVH: new (2007-SEP-21)
related: Seyfert galaxy
related: quasar

line shift
type: Concept
alternative label: spectral line shift
definition: line shift
narrower: blueshift
narrower: redshift
related: Doppler effect
related: Zeeman splitting
related: radial velocity

line spectrum
type: Concept
definition: line spectrum
narrower: absorption spectrum
narrower: emission spectrum
related: Voigt profile
related: pressure broadening
related: ultraviolet line

line width
type: Concept
alternative label: spectral line width
definition: line width
narrower: equivalent width
narrower: natural line width
related: Doppler broadening
related: Milne Eddington approximation
related: Tully-Fisher relation
related: g value
related: gf value
related: instrumental profile
related: line broadening
related: oscillator strength
related: spectral type
related: stellar atmosphere
related: surface gravity
related: transition probability

lithium
type: Concept
alternative label: Li
broader: fundamental chemical element
definition: lithium (atomic number 3)
history note: FVH: new (2007-OCT-25)
related: lithium-poor star
related: lithium star

lithium-poor star
type: Concept
alternative label: lithium poor star
broader: metal-poor star
definition: lithium-poor star
related: lithium

lithium star
type: Concept
alternative label: Li star
alternative label: lithium rich star
alternative label: lithium-rich star
broader: star
definition: lithium star
related: giant
related: lithium

lithosphere
type: Concept
definition: lithosphere
related: mantle
related: planet

L magnitude
type: Concept
broader: apparent magnitude
definition: L magnitude
related: infrared photometry
related: near infrared radiation

lobe
type: Concept
broader: radio structure
definition: lobe
related: radio source
scope note: radio source feature

Local Group
type: Concept
broader: galaxy group
broader: nearby galaxy
definition: Local Group of galaxies
narrower: Magellanic cloud
narrower: Milky Way galaxy
related: bright galaxy

Local Standard of Rest
type: Concept
alternative label: L.S.R.
alternative label: LSR
definition: Local Standard of Rest
related: Sun
related: orbit
related: peculiar motion
related: peculiar velocity
related: proper motion
related: stellar motion

Local Supercluster
type: Concept
broader: galaxy cluster
definition: Local Supercluster of galaxies
related: Great Attractor
related: galaxy

local thermodynamic equilibrium
type: Concept
alternative label: LTE
broader: thermodynamic equilibrium
definition: local thermodynamic equilibrium
related: non-LTE transfer
related: thermal equilibrium
related: thermal instability
related: thermal stability
related: thermodynamics

location behind
type: Concept
broader: location
definition: location behind something else
history note: FVH: new (2007-SEP-21)
related: line of sight
related: location between
related: location in front

location between
type: Concept
broader: location
definition: location between
history note: FVH: new (2007-SEP-21)
related: line of sight
related: location behind
related: location in front

location in front
type: Concept
broader: location
definition: location in front of something else
history note: FVH: new (2007-SEP-21)
related: line of sight
related: location behind
related: location between

location
type: Concept
definition: having to do with cosmic location
history note: FVH: new (2007-SEP-21)
narrower: line of sight
narrower: location behind
narrower: location between
narrower: location in front

log g value
type: Concept
broader: g value
definition: log(g) value
history note: ES: new (2007-OCT-8)
history note: logarithm reference needed!
related: gf value

long baseline interferometer
type: Concept
broader: interferometer
broader: radio interferometer
definition: long baseline interferometer
related: optical interferometer
related: very long baseline interferometer

long baseline interferometry
type: Concept
broader: interferometry
broader: radio interferometry
definition: long baseline interferometry
related: optical interferometry
related: radio astrometry
related: very long baseline interferometry

longitude
type: Concept
definition: longitude
narrower: Galactic longitude
narrower: Right Ascension
narrower: ecliptic longitude
narrower: supergalactic longitude
scope note: on celestial sphere

long period comet
type: Concept
broader: comet
definition: long period comet

long period variable star
type: Concept
broader: pulsating variable star
definition: long period variable star
narrower: Mira variable star
narrower: RV Tauri star
narrower: S Vulpeculae star
narrower: WZ Sagittae star
related: late-type supergiant

long slit
type: Concept
broader: spectrograph slit
definition: long slit
history note: FVH: new (2007-OCT-3)

long slit spectrum
type: Concept
change note: FVH: added RT SPECTROGRAPH_SLITS (2007-SEP-21)
definition: long slit spectrum
related: spectrograph slit
related: three-dimensional spectrum
related: two-dimensional spectrum

loop
type: Concept
definition: loop
scope note: combine with other terms

low-luminosity star
type: Concept
alternative label: low luminosity star
broader: star
definition: low-luminosity star
narrower: late-type dwarf
narrower: late-type subdwarf
related: dwarf
related: low-mass star

low-mass star
type: Concept
alternative label: low mass star
broader: star
change note: FVH+ES: moved brown_dwarf to RT (2007-OCT-11)
definition: low-mass star
narrower: HZ Herculis star
narrower: black dwarf
related: T dwarf
related: brown dwarf
related: dwarf
related: low-luminosity star
related: low-mass X-ray binary star

low-mass X-ray binary star
type: Concept
alternative label: LMXB
broader: X-ray binary star
definition: low-mass X-ray binary star
related: accretion disk
related: cataclysmic variable star
related: high-mass X-ray binary star
related: low-mass star
related: neutron star

low-state
type: Concept
definition: photometric low state of variable object
history note: FVH: new (2007-OCT-8)
related: high-state
related: outburst
related: variability
related: variable source

low-temperature plasma
type: Concept
broader: plasma
definition: low temperature plasma

L subdwarf
type: Concept
broader: brown dwarf
broader: late-type subdwarf
broader: subdwarf
definition: L subdwarf
history note: FVH: new (2007-OCT-9)
related: L dwarf

luminescence
type: Concept
alternative label: candoluminescence
definition: luminescence
narrower: chemiluminescence
narrower: thermoluminescence
related: afterglow
related: electromagnetic radiation
related: fluorescence
related: light emission
related: light scattering
related: noctilucent cloud
related: visible radiation

luminosity classification
type: Concept
broader: classification
definition: luminosity classification
related: dwarf
related: giant
related: luminosity class
related: spectral classification
related: spectral type
related: subgiant
related: surface gravity

luminosity class
type: Concept
broader: MK classification
definition: luminosity class
related: luminosity
related: luminosity classification
related: spectral type
scope note: see: luminosity classification

luminosity-dispersion relation
type: Concept
broader: correlation
definition: luminosity-dispersion relation
history note: FVH: new (2007-OCT-9)
narrower: Faber-Jackson relation
narrower: fundamental plane
related: luminosity
related: velocity dispersion

luminosity distribution
type: Concept
definition: luminosity distribution
related: brightness temperature
related: isophot
related: isophotal diameter

luminosity function
type: Concept
definition: luminosity function
related: galaxy
related: galaxy cluster
related: star cluster
related: stellar evolution

luminosity
type: Concept
change note: FVH: removed UF absolute_intensity as unphysical misnomer (2007-SEP-24)
definition: luminosity
narrower: X-ray luminosity
narrower: ultraviolet luminosity
related: Hertzsprung-Russell diagram
related: MK classification
related: absolute magnitude
related: brightness
related: flux
related: flux density
related: intensity
related: luminosity class
related: luminosity-dispersion relation
related: mass to light ratio
related: surface gravity

luminous arc
type: Concept
broader: arc
broader: gravitationally lensed source
change note: FVH: changed UF arc to BT ARCS and QUASARS to CLUSTERS_OF_GALAXIES (2007-OCT-1)
change note: FVH: moved BT arc to RT arc and added BT gravitationally_lensed_source (2007-OCT-8)
definition: luminous arc produced by gravitational lensing
related: galaxy cluster
related: gravitational lensing
related: quasar

luminous blue variable star
type: Concept
broader: early-type variable star
broader: high-luminosity star
definition: luminous blue variable star
related: early-type supergiant

lunar dome
type: Concept
definition: lunar dome
related: Moon
related: surface of celestial body

lunar eclipse
type: Concept
broader: eclipse
definition: lunar eclipse
related: Moon
related: Saros cycle
related: Sun
related: penumbra
related: umbra

lunar laser ranging
type: Concept
broader: laser ranging
definition: lunar laser ranging
related: Moon
related: laser
related: optical radar
related: satellite laser ranging

lunar
type: Concept
definition: lunar
scope note: combine lunar or Moon with other terms; also see Moon

lunar occultation
type: Concept
broader: occultation
definition: occultation by the Moon
history note: FVH: new (2007-OCT-8)
related: Moon

lunar phase
type: Concept
alternative label: phase Moon
definition: phase of the Moon
related: Saros cycle
related: illumination
related: metonic cycle
related: phase angle
related: phase defect
related: phase effect
related: terminator line

lunar theory
type: Concept
definition: lunar theory
related: Earth-Moon system
related: Moon
related: celestial mechanics

lutetium
type: Concept
alternative label: Lu
broader: fundamental chemical element
broader: rare earth
definition: lutetium (atomic number 71)
history note: FVH: new (2007-OCT-25)

Lyman alpha
type: Concept
broader: Lyman series
broader: resonance line
definition: Lyman alpha
related: Lyman alpha forest

Lyman alpha forest
type: Concept
definition: Lyman alpha forest
related: Lyman alpha
related: absorption line
related: intergalactic absorption
related: quasar
related: redshift

Lyman beta
type: Concept
broader: Lyman series
definition: Lyman beta

Lyman continuum
type: Concept
broader: hydrogen spectrum
definition: Lyman continuum
related: ultraviolet radiation

Lyman series
type: Concept
broader: hydrogen spectrum
definition: Lyman series
narrower: Lyman alpha
narrower: Lyman beta
related: Balmer series
related: Brackett series
related: Paschen series
related: Pfund series
related: ultraviolet radiation

macro spicule
type: Concept
broader: spicule
definition: macro spicule
related: Sun
related: chromosphere

macroturbulence
type: Concept
broader: turbulence Earth atmosphere
broader: turbulence star atmosphere
definition: macroturbulence
related: atmosphere
related: stellar structure

Magellanic cloud
type: Concept
alternative label: Clouds of Magellan
broader: Local Group
broader: galaxy
broader: irregular galaxy
broader: nearby galaxy
definition: Magellanic cloud
narrower: Large Magellanic Cloud
narrower: Small Magellanic Cloud
related: Magellanic stream

Magellanic stream
type: Concept
definition: Magellanic stream
related: Magellanic cloud

magnesium
type: Concept
alternative label: Mg
broader: fundamental chemical element
definition: magnesium (atomic number 12)
history note: FVH: new (2007-OCT-25)

magnetar
type: Concept
broader: magnetic star
broader: neutron star
definition: magnetar
history note: ES: new (2007-OCT-8)
narrower: soft gamma-ray repeater

magnetic anomaly
type: Concept
broader: anomaly
definition: magnetic anomaly
related: gravity anomaly
related: magnetic property

magnetic disturbances
type: Concept
definition: magnetic disturbances
related: aurora
related: magnetic property

magnetic field
type: Concept
definition: magnetic field
narrower: emerging flux
narrower: geomagnetic field
narrower: interplanetary magnetic field
narrower: interstellar magnetic field
related: Paschen-Back effect
related: dynamo theory
related: force
related: magnetic monopole
related: magnetic pole
related: magnetic property
related: magnetic variable star
related: magnetohydrodynamics
related: magnetosphere
related: paleomagnetism
related: sunspot

magnetic monopole
type: Concept
definition: magnetic monopole
related: magnetic field
related: magnetic pole

magnetic pole
type: Concept
definition: magnetic pole
related: aurora
related: magnetic field
related: magnetic monopole
related: magnetic storm
related: magnetic variable star

magnetic property
type: Concept
broader: property
definition: magnetic property
related: magnetic anomaly
related: magnetic disturbances
related: magnetic field
related: magnetic star

magnetic star
type: Concept
alternative label: cobalt star
broader: peculiar star
definition: magnetic star
narrower: Am star
narrower: Bp star
narrower: magnetar
narrower: magnetic variable star
narrower: manganese star
narrower: mercury manganese star
related: Ap star
related: cobalt
related: magnetic property
related: oblique rotator
related: spectrum variable star
related: strontium star

magnetic storm
type: Concept
definition: magnetic storm
narrower: magnetospheric substorm
related: aurora
related: magnetic pole
related: magnetosphere
related: solar activity
related: sunspot

magnetic variable star
type: Concept
broader: intrinsic variable star
broader: magnetic star
definition: magnetic variable star
narrower: Am star
narrower: SX Arietis star
narrower: alpha2 Canum Venaticorum star
related: Ap star
related: magnetic field
related: magnetic pole

magnetograph
type: Concept
broader: instrument
definition: magnetograph

magnetoheliograph
type: Concept
broader: instrument
definition: magnetoheliograph

magnetohydrodynamics
type: Concept
alternative label: MHD
alternative label: hydromagnetics
change note: FVH: moved mhd to ALT, ALFVEN_WAVES to NT (2007-SEP-24)
definition: magnetohydrodynamics
narrower: Alfven wave
related: cosmic electrodynamics
related: hydrodynamics
related: magnetic field
related: plasma physics
related: plasma wave
related: synchrotron radiation
related: van Allen radiation belt

magneto-optical effect
type: Concept
alternative label: magneto optical effect
definition: magneto-optical effect
narrower: Faraday effect
narrower: Zeeman splitting
narrower: polarization charge separation

magnetosphere
type: Concept
definition: magnetosphere
related: Earth atmosphere
related: exosphere
related: magnetic field
related: magnetic storm
related: magnetospheric substorm
related: upper atmosphere

magnetospheric substorm
type: Concept
broader: magnetic storm
definition: magnetospheric substorm
related: magnetosphere

magnitude
type: Concept
definition: magnitude
narrower: absolute magnitude
narrower: apparent magnitude
narrower: integrated magnitude
related: Pogson scale
related: amplitude
related: brightness
related: intensity
related: light curve
related: photometry
scope note: also see under apparent magnitude

main sequence
type: Concept
definition: main sequence
related: Hertzsprung-Russell diagram
related: dwarf
related: main sequence star
related: turnoff point
related: zero-age main sequence

main sequence star
type: Concept
broader: star
definition: main sequence star
narrower: blue straggler star
narrower: dwarf
related: main sequence
related: mass-luminosity relation
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

major axis
type: Concept
broader: semimajor axis
definition: major axis
related: axial ratio
related: minor axis
scope note: see terms under semimajor axis

Maksutov telescope
type: Concept
broader: catadioptric system
broader: reflecting telescope
definition: Maksutov telescope
related: Bouwers telescope
related: Schmidt telescope
related: wide-field telescope

manganese
type: Concept
alternative label: Mn
broader: fundamental chemical element
definition: manganese (atomic number 25)
history note: FVH: new (2007-OCT-25)
related: manganese star
related: mercury manganese star

manganese star
type: Concept
broader: Ap star
broader: magnetic star
broader: spectrum variable star
definition: manganese star
related: manganese

mantle
type: Concept
definition: mantle
related: Earth
related: Moon
related: crust
related: crustal dynamics
related: lithosphere
related: planet

map
type: Concept
definition: map
narrower: X-ray map
narrower: contour map
related: atlas
related: catalog
related: finding chart
related: photogrammetry
related: planet
related: radar mapping
related: sky survey
related: star atlas

maria
type: Concept
definition: maria
related: Moon
related: surface of celestial body

Markarian galaxy
type: Concept
broader: emission line galaxy
definition: Markarian galaxy
related: Seyfert galaxy
related: peculiar galaxy

Mars
type: Concept
broader: planet
definition: Mars
history note: FVH: new (2007-SEP-24)
related: Solar System

mascon
type: Concept
definition: mascon
related: Moon
related: gravity anomaly

maser
type: Concept
definition: maser
narrower: OH maser
narrower: SiO maser
narrower: megamaser
narrower: water maser
related: coherence
related: electron pumping
related: interstellar matter
related: inverse maser
related: laser
related: population inversion
related: radio recombination line
related: radio source
related: stimulated emission

mass density
type: Concept
broader: density
change note: FVH: added NT OMEGA_PARAMETER (2007-SEP-21)
definition: mass-density
related: Omega baryon
related: Omega mass
related: Omega parameter
related: mass

mass distribution
type: Concept
definition: mass distribution
history note: FVH: new (2007-OCT-5)
narrower: Burkert profile
narrower: Navarro-Frenk-White profile
narrower: exponential profile
narrower: isothermal sphere
related: Dark Matter
related: disk galaxy
related: galaxy
related: galaxy cluster
related: galaxy rotation curve
related: galaxy structure
related: gravitational lensing

mass exchange
type: Concept
alternative label: exchange of mass
definition: mass-exchange
related: cataclysmic variable star
related: contact binary star
related: eruptive binary star
related: mass
related: mass flow
related: mass-loss
related: mass-transfer

mass flow
type: Concept
definition: mass-flow
related: mass
related: mass exchange
related: mass-loss
related: mass-transfer

mass function
type: Concept
definition: mass-function
related: birth rate
related: mass
related: mass-ratio
related: spectroscopic binary star
related: star cluster
related: star count

massive galaxy
type: Concept
broader: galaxy
definition: massive galaxy
narrower: cD galaxy
related: D galaxy
related: galaxy cluster

massive object
type: Concept
definition: massive object
related: Seyfert galaxy
related: black hole
related: galactic nucleus

massive star
type: Concept
broader: star
definition: massive star
related: mass-loss
related: supermassive star

mass-loss
type: Concept
alternative label: mass loss
alternative label: mass-ejection
definition: mass-loss
narrower: bipolar outflow
narrower: coronal mass ejection
narrower: jet
narrower: stellar wind
related: FU Orionis star
related: P Cygni line profile
related: Wolf-Rayet star
related: binary star
related: cataclysmic variable star
related: circumstellar disk
related: circumstellar envelope
related: circumstellar matter
related: circumstellar shell
related: corona
related: eruptive binary star
related: mass exchange
related: mass flow
related: mass-transfer
related: massive star
related: nova
related: planetary nebula
related: stellar evolution
related: supernova

mass-luminosity relation
type: Concept
alternative label: mass luminosity relation
broader: statistical relation
definition: mass-luminosity relation
related: main sequence star

mass
type: Concept
definition: mass
narrower: Chandrasekhar mass
narrower: Chandrasekhar-Schoenberg limit
related: gravitation
related: initial mass function
related: mass density
related: mass exchange
related: mass flow
related: mass function
related: mass to light ratio
related: momentum
related: spectroscopic binary star
related: surface gravity

mass-radius relation
type: Concept
alternative label: mass radius relation
broader: statistical relation
definition: mass-radius relation
related: Chandrasekhar mass
related: Chandrasekhar-Schoenberg limit
related: degenerate star

mass-ratio
type: Concept
alternative label: mass ratio
definition: mass-ratio
related: binary star
related: initial mass function
related: mass function

mass to light ratio
type: Concept
definition: mass-to-light ratio
related: galaxy
related: luminosity
related: mass
related: missing mass

mass-transfer
type: Concept
alternative label: mass transfer
definition: mass-transfer
related: accretion
related: convection
related: fluid dynamics
related: mass exchange
related: mass flow
related: mass-loss

mathematical analysis
type: Concept
definition: mathematical analysis
narrower: differential equation
related: catastrophe theory
scope note: combine with other terms

mathematical model
type: Concept
change note: FVH: changed COMPUTER_MODELS from U to RT (2007-SEP-21)
definition: mathematical model
related: computer model

mathematics
type: Concept
broader: scientific field
definition: mathematics
scope note: combine with other terms

matter
type: Concept
definition: matter
narrower: antimatter
narrower: atom
narrower: circumplanetary matter
narrower: circumstellar matter
narrower: degenerate matter
narrower: molecule

Maunder minimum
type: Concept
definition: Maunder minimum
related: solar activity
related: sunspot cycle
related: sunspot number

maximum entropy method
type: Concept
definition: maximum entropy method
related: Fourier analysis
related: frequency analysis
related: spectroscopic analysis

maximum
type: Concept
broader: photometric element
definition: maximum
related: light curve
related: minimum
related: variable star
related: velocity curve

M dwarf
type: Concept
broader: M star
broader: dwarf
broader: late-type dwarf
definition: M dwarf star

mean anomaly
type: Concept
broader: orbital anomaly
definition: mean anomaly

mean equinox
type: Concept
broader: equinox
definition: mean equinox
related: planet

mean solar time
type: Concept
broader: time
definition: mean solar time
related: Universal Time
related: civil time
related: ephemeris time
related: equation of time

measurement
type: Concept
definition: measurement
related: determination
related: measuring instrument
related: metrology
related: quantization
scope note: combine with other terms

measuring instrument
type: Concept
definition: measuring instrument
narrower: altimeter
narrower: anemometer
narrower: atomic clock
narrower: barometer
narrower: chronometer
narrower: clock
narrower: counter
narrower: densitometer
narrower: heliometer
narrower: microdensitometer
narrower: micrometer
narrower: microphotometer
narrower: monochromator
narrower: proportional counter
narrower: radiometer
narrower: range finder
narrower: sensitometer
narrower: weather station
narrower: wind vane
related: calibration
related: measurement

mechanical component
type: Concept
definition: mechanical component
scope note: combine with other terms

mechanical property
type: Concept
broader: property
definition: mechanical property
scope note: combine with other terms

medium band photometry
type: Concept
broader: CCD photometry
broader: photoelectric photometry
definition: medium-band photometry
narrower: DDO photometry
narrower: Geneva photometry
narrower: Stromgren photometry
narrower: Vilnius photometry
narrower: Walraven photometry
narrower: infrared photometry
narrower: ultraviolet photometry
related: broad band photometry
related: narrow band photometry

megalithic astronomy
type: Concept
broader: archaeoastronomy
definition: megalithic astronomy

megamaser
type: Concept
broader: maser
definition: megamaser

meitnerium
type: Concept
alternative label: Mt
broader: fundamental chemical element
definition: meitnerium (atomic number 109)
history note: FVH: new (2007-OCT-25)

mendelevium
type: Concept
alternative label: Md
broader: fundamental chemical element
definition: mendelevium (atomic number 101)
history note: FVH: new (2007-OCT-25)

Mercury
type: Concept
broader: planet
definition: the planet Mercury
history note: FVH: new (2007-SEP-24)
related: Solar System
scope note: See mercury for the element rather than the planet.

mercury manganese star
type: Concept
broader: B star
broader: magnetic star
definition: mercury manganese star
related: manganese
related: mercury

mercury
type: Concept
alternative label: Hg
broader: fundamental chemical element
definition: mercury (atomic number 80)
related: mercury manganese star
scope note: Don't get confused with the planet Mercury (2007-NOV-13)

merger
type: Concept
definition: merger
narrower: galaxy merger

meridian circle
type: Concept
broader: transit instrument
definition: meridian circle
related: astrometry
related: meridian
related: quadrant
related: vertical circle

meridian
type: Concept
definition: meridian
history note: FVH: new (2007-OCT-3)
related: celestial sphere
related: horizon coordinate system
related: meridian circle
related: meridian observation

meridian observation
type: Concept
definition: meridian observation
related: meridian
related: transit instrument
related: transit telescope
related: transit time
related: zenith telescope

meson
type: Concept
broader: boson
broader: elementary particle
definition: meson
related: photon
related: quark

mesopause
type: Concept
definition: mesopause
related: Earth atmosphere
related: ionosphere
related: mesosphere
related: thermosphere

mesosphere
type: Concept
definition: mesosphere
related: Earth atmosphere
related: mesopause
related: stratopause
related: upper atmosphere

Me star
type: Concept
broader: M star
broader: emission line star
definition: Me star
related: Me variable star
related: late-type variable star

metagalaxy
type: Concept
definition: metagalaxy
related: universe

metal abundance
type: Concept
alternative label: metallicity
broader: abundance
definition: metal abundance
related: CNO anomaly
related: Oosterhoff group
related: chemical element
related: dredge up
related: helium-poor star
related: helium-rich star
related: hydrogen deficient star
related: metal-deficient star
related: metal-poor star
related: metal-rich star
related: rare earth
related: trace element

metal-deficient star
type: Concept
broader: star
definition: metal-deficient star
related: metal abundance
related: metal-poor star
related: ultraviolet excess star

metal line
type: Concept
broader: spectral line
definition: metal line
narrower: Ca II emission line
narrower: calcium line
narrower: carbon line
narrower: technetium line
related: absorption line
related: line blanketing
related: rare earth

metal-poor star
type: Concept
alternative label: metal poor star
broader: star
change note: FVH: added NT POP II and III STARS (2007-SEP-21)
definition: metal-poor star
narrower: lithium-poor star
narrower: population II star
narrower: population III star
narrower: weak G band star
related: metal abundance
related: metal-deficient star
related: ultraviolet excess star

metal-rich star
type: Concept
alternative label: metallic line star
broader: star
definition: metal rich star
narrower: Am star
narrower: silicon star
related: metal abundance
related: red giant bump

meteor camera
type: Concept
definition: meteor camera
narrower: Baker-Nunn camera

meteorite crater
type: Concept
definition: meteorite crater
related: meteor
related: meteorite
related: meteorite impact

meteorite impact
type: Concept
definition: meteorite impact
related: meteor
related: meteorite
related: meteorite crater

meteorite
type: Concept
broader: meteor
definition: meteorite
narrower: achondrite
narrower: aerolite
narrower: ataxite
narrower: australite
narrower: bediasite
narrower: chondrite
narrower: iron meteorite
narrower: micrometeorite
narrower: moldavite
narrower: tektite
related: Neumann line
related: ablation
related: asteroid
related: collision
related: comet
related: impact crater
related: interplanetary matter
related: meteorite crater
related: meteorite impact

meteor
type: Concept
definition: meteor
narrower: bolide
narrower: fireball
narrower: meteorite
related: crater
related: meteor shower
related: meteor stream
related: meteor trail
related: meteorite crater
related: meteorite impact
related: meteoroid
related: meteoroid dust cloud
related: radiant meteor

meteoroid dust cloud
type: Concept
definition: meteoroid dust cloud
related: asteroid
related: comet
related: meteor
related: meteoroid
related: zodiacal dust

meteoroid
type: Concept
alternative label: meteorids
broader: interplanetary dust
broader: interplanetary grain
broader: interplanetary matter
definition: meteoroid
narrower: micrometeoroid
related: asteroid
related: comet
related: meteor
related: meteoroid dust cloud
related: zodiacal dust

meteorology
type: Concept
definition: meteorology
related: Earth atmosphere

meteor shower
type: Concept
definition: meteor shower
related: meteor
related: meteor stream
related: meteor trail
related: radiant meteor
related: zenith hourly rate
scope note: named shower not included

meteor stream
type: Concept
definition: meteor stream
related: asteroid
related: comet
related: meteor
related: meteor shower
related: meteor trail
related: radiant meteor

meteor trail
type: Concept
definition: meteor trail
related: meteor
related: meteor shower
related: meteor stream
related: radiant meteor

methane
type: Concept
alternative label: CH4
alternative label: CH_4
broader: interstellar molecule
broader: molecule
definition: methane molecule
history note: FVH: new (2007-OCT-5)
related: molecular cloud

metonic cycle
type: Concept
definition: metonic cycle
related: Saros cycle
related: lunar phase

metrology
type: Concept
definition: metrology
related: instrument
related: measurement
related: unit

Me variable star
type: Concept
broader: M giant
broader: emission line star
broader: late-type variable star
definition: Me variable star
related: Me star

M giant
type: Concept
broader: M star
broader: giant
broader: late-type giant
definition: M giant star
narrower: Me variable star
related: M subgiant

Michelson interferometer
type: Concept
broader: optical interferometer
definition: Michelson interferometer
related: Michelson interferometry
related: intensity interferometer

Michelson interferometry
type: Concept
definition: Michelson interferometry
related: Michelson interferometer
related: optical interferometry

microchannel plate
type: Concept
broader: amplifier
definition: micro-channel plate
history note: FVH: new (2007-SEP-21)
related: image tube

microdensitometer
type: Concept
broader: measuring instrument
definition: microdensitometer
related: densitometer
related: microphotometer
related: photograph

microdensitometry
type: Concept
definition: microdensitometry
scope note: see microdensitometer

micrometeorite
type: Concept
broader: meteorite
definition: micrometeorite
related: interplanetary matter

micrometeoroid
type: Concept
broader: meteoroid
definition: micrometeoroid

micrometer
type: Concept
broader: measuring instrument
definition: micrometer

microphotometer
type: Concept
broader: measuring instrument
definition: microphotometer
related: microdensitometer
related: photography

microprocessor
type: Concept
broader: computer
definition: microprocessor
related: control system

microturbulence
type: Concept
broader: turbulence Earth atmosphere
broader: turbulence star atmosphere
definition: microturbulence
related: absorption line
related: atmosphere

microwave antenna
type: Concept
alternative label: microwave antennas
broader: antenna
definition: microwave antennaa
related: microwave radiation

microwave background
type: Concept
broader: background radiation
broader: cosmic noise
broader: microwave radiation
change note: FVH: Added RT COSMOLOGY (2007-SEP-21)
definition: cosmic microwave background
related: Sunyaev-Zeldovich effect
related: X-ray background
related: cosmology
related: gamma-ray background
related: radio background
related: ultraviolet background

microwave emission
type: Concept
broader: emission spectrum
definition: microwave emission
related: cosmic noise

microwave imaging
type: Concept
definition: microwave imaging
related: microwave radiation

microwave
type: Concept
definition: microwave
related: millimeter radiation
scope note: combine with other terms

microwave radiation
type: Concept
broader: electromagnetic radiation
definition: microwave radiation
narrower: microwave background
related: microwave antenna
related: microwave imaging
related: millimeter radiation
related: remote sensing

microwave spectroscopy
type: Concept
broader: spectroscopy
definition: microwave spectroscopy

microwave spectrum
type: Concept
broader: spectrum
definition: microwave spectrum
related: radio spectrum

Mie scattering
type: Concept
broader: scattering
definition: Mie scattering
related: Rayleigh scattering
related: brillouin scattering

Milky Way galaxy
type: Concept
alternative label: the Galaxy
broader: Local Group
broader: galaxy
broader: spiral galaxy
definition: the Milky Way galaxy
related: Galactic anticenter
related: Galactic bulge
related: Galactic center
related: Galactic cluster
related: Galactic coordinate system
related: Galactic cosmic ray
related: Galactic equator
related: Galactic halo
related: Galactic latitude
related: Galactic longitude
related: Galactic plane
related: Galactic pole
related: Galactic rotation
related: Goulds belt
related: high-velocity cloud
related: high-velocity star
related: sky brightness

millimeter astronomy
type: Concept
broader: radio astronomy
definition: millimeter astronomy
related: radio observatory
related: satellite-borne instrument
related: submillimeter astronomy

millimeter radiation
type: Concept
alternative label: millimeter wave
alternative label: mm radiation
broader: electromagnetic radiation
change note: FVH: added BT electromagnetic_radiation (2007-OCT-8)
definition: millimeter radiation
related: microwave
related: microwave radiation

Mills cross antenna
type: Concept
alternative label: Mills cross antennas
broader: antenna
broader: directional antenna
broader: radio telescope
definition: Mills cross antenna
related: pencil beam

Milne Eddington approximation
type: Concept
definition: Milne Eddington approximation
related: line width
related: spectroscopic analysis

mineral deposit
type: Concept
definition: mineral deposit
related: mineralogy

mineralogy
type: Concept
definition: mineralogy
related: mineral deposit

minimum
type: Concept
broader: photometric element
definition: minimum
related: light curve
related: maximum
related: variable star
related: velocity curve

minor axis
type: Concept
broader: semiminor axis
definition: minor axis
history note: ES: new (2007-OCT-11)
history note: see terms under major axis
related: axial ratio
related: major axis

minor planet family
type: Concept
definition: minor planet family
narrower: Amor group
narrower: Apollo group
narrower: Hirayama family
narrower: Trojan group
related: asteroid
scope note: not a complete list of terms

Mira variable star
type: Concept
alternative label: Miras
alternative label: omicron Ceti star
alternative label: zeta Aurigae star
broader: emission line star
broader: irregular variable star
broader: late-type giant
broader: long period variable star
broader: pulsating variable star
definition: Mira variable star
related: S Vulpeculae star
related: radial pulsation
related: semi-regular variable star

mirror cell
type: Concept
definition: mirror cell
related: mirror

mirror
type: Concept
broader: optical component
definition: mirror
narrower: dichroic mirror
narrower: primary mirror
narrower: telescope mirror
related: aluminizing
related: aluminum coating
related: catadioptric system
related: catoptric system
related: coating
related: collimator
related: figuring
related: glass
related: mirror cell
related: optical aberration
related: optical instrument
related: optical material
related: optical surface
related: polishing
related: reflection
related: thin film

missing mass
type: Concept
definition: missing mass
related: cosmology
related: galaxy cluster
related: mass to light ratio
related: velocity dispersion

MK classification
type: Concept
broader: spectral classification
definition: MK classification
narrower: luminosity class
related: luminosity
related: spectrum

M magnitude
type: Concept
broader: apparent magnitude
definition: M magnitude
related: far infrared radiation
related: infrared photometry

model
type: Concept
definition: model
narrower: computer model
narrower: orrery
related: equilibrium figures
related: numerical simulation
related: polytrope
related: simulation
related: stellar structure
scope note: combine with other terms

MOdified Newtonian Dynamics
type: Concept
alternative label: MOND
broader: gravitation
definition: MOdified Newtonian Dynamics
related: Newtonian gravitation
related: gravitational effect
related: gravitational force

modulation
type: Concept
definition: modulation
scope note: combine with other terms

modulation transfer function
type: Concept
alternative label: MTF
broader: transfer function
definition: modulation transfer function
related: optical instrument
related: optical testing
related: optical transfer function

moldavite
type: Concept
broader: meteorite
broader: tektite
definition: moldavite
related: australite
related: bediasite
related: chondrite

molecular astrophysics
type: Concept
definition: molecular astrophysics
related: cosmochemistry
related: molecular band
related: molecular line
related: molecular spectroscopy

molecular band
type: Concept
broader: spectral band
definition: molecular band
narrower: B band
narrower: G band
narrower: Phillips band
narrower: Swan band
related: late-type star
related: molecular astrophysics
related: molecular line
related: molecular spectrum
related: zirconium star

molecular cloud
type: Concept
broader: interstellar matter
definition: molecular cloud
narrower: giant molecular cloud
related: interstellar molecule
related: methane
related: molecular hydrogen

molecular hydrogen
type: Concept
broader: hydrogen
broader: interstellar molecule
broader: molecule
definition: molecular hydrogen
narrower: orthohydrogen
narrower: parahydrogen
related: molecular cloud

molecular line
type: Concept
broader: spectral line
definition: molecular line
related: fine structure
related: late-type star
related: molecular astrophysics
related: molecular band
related: spectral band

molecular spectroscopy
type: Concept
definition: molecular spectroscopy
related: molecular astrophysics
scope note: see molecular spectrum

molecular spectrum
type: Concept
broader: spectrum
definition: molecular spectrum
narrower: Phillips band
narrower: p branch
related: B band
related: G band
related: Raman spectroscopy
related: Swan band
related: late-type star
related: molecular band
related: molecule
related: organic molecule
related: q branch
related: spectral band
related: vibrational spectrum

molecule
type: Concept
broader: matter
definition: molecule
narrower: hydrated carbon
narrower: interstellar molecule
narrower: methane
narrower: molecular hydrogen
narrower: organic molecule
related: molecular spectrum

molybdenum
type: Concept
alternative label: Mo
broader: fundamental chemical element
definition: molybdenum (atomic number 42)
history note: FVH: new (2007-OCT-25)

momentum
type: Concept
definition: momentum
related: angular momentum
related: mass
related: velocity

monochromator
type: Concept
broader: measuring instrument
broader: optical instrument
definition: monochromator

Monte Carlo technique
type: Concept
broader: data processing
definition: Monte Carlo technique
related: statistics

Moon
type: Concept
broader: satellite
definition: Moon
related: Earthshine
related: anomalistic month
related: apogee
related: crater
related: crust
related: crustal dynamics
related: equation of the center
related: libration
related: lunar dome
related: lunar eclipse
related: lunar laser ranging
related: lunar occultation
related: lunar theory
related: mantle
related: maria
related: mascon
related: moonquake
related: nutation
related: occultation
related: perigee
related: phase angle
related: phase defect
related: ray
related: regression of node
related: selenology
related: solar eclipse
related: surface of celestial body
scope note: Earth's satellite; see under satellite or planet for more rts; see also lunar

moonquake
type: Concept
definition: moonquake
related: Moon
related: earthquake

morphology
type: Concept
definition: morphology
related: classification
related: disk flaring
scope note: combine with other terms

motion
type: Concept
definition: motion
narrower: apparent superluminal motion
narrower: apsidal motion
narrower: internal motion
narrower: orbital motion
narrower: polar motion
narrower: proper motion
narrower: solar motion
narrower: space motion
narrower: stellar motion
narrower: wave motion
related: orbit
related: orrery
related: planetarium
scope note: combine with other terms

mottle
type: Concept
definition: mottle
related: Sun
related: chromosphere

moving cluster parallax
type: Concept
alternative label: cluster parallax
broader: parallax
definition: moving cluster parallax
related: dynamical parallax
related: kinematic parallax
related: open star cluster
related: proper motion
related: radiant moving cluster
related: secular parallax

m region
type: Concept
broader: solar corona
definition: m region

M star
type: Concept
broader: late-type star
definition: M star
narrower: M dwarf
narrower: M giant
narrower: M subdwarf
narrower: M subgiant
narrower: M supergiant
narrower: Me star
related: spectral type
related: titanium oxide

M subdwarf
type: Concept
broader: M star
broader: subdwarf
definition: M subdwarf star

M subgiant
type: Concept
broader: M star
broader: subgiant
definition: M subgiant star
related: M giant

M supergiant
type: Concept
broader: M star
broader: late-type supergiant
definition: M supergiant star

multi-channel detector
type: Concept
alternative label: multichannel detector
broader: detector
definition: multi-channel detector
narrower: CCD detector
narrower: diode array
narrower: image tube
narrower: reticon array
narrower: television detector
related: charge-coupled device
related: multi-channel spectrograph

multi-channel spectrograph
type: Concept
alternative label: multi-channel spectrometer
alternative label: multichannel spectrograph
broader: spectrograph
definition: multi-channel spectrograph
related: multi-channel detector

multi-color photometry
type: Concept
alternative label: multicolor photometry
broader: photometry
definition: multi-color photometry

multi-fiber spectrograph
type: Concept
broader: spectrograph
definition: multi-fiber spectrograph
history note: FVH: new (2007-SEP-21)
related: integral field spectrograph
related: optical fiber
related: three-dimensional spectrum

multi-periodic pulsation
type: Concept
alternative label: multiperiodic pulsation
definition: multi-periodic pulsation
narrower: double-mode pulsation
related: Fourier analysis
related: frequency analysis
related: multi-periodic variable star
related: pulsating variable star
related: pulsation mode

multi-periodic variable star
type: Concept
alternative label: multiperiodic variable star
broader: periodic variable star
broader: pulsating variable star
definition: multi-periodic variable star
narrower: PG1159 star
narrower: RS Canum Venaticorum star
narrower: SX Phoenicis star
narrower: ZZ Ceti star
narrower: beta Cephei star
narrower: delta Scuti star
narrower: double-mode variable star
narrower: dwarf Cepheid
related: multi-periodic pulsation
related: overtone frequency
related: overtone mode
related: pulsation mode

multiple galaxy
type: Concept
broader: galaxy
definition: multiple galaxy
related: galaxy cluster
related: galaxy group

multiple mirror telescope
type: Concept
alternative label: MMT
broader: optical telescope
broader: reflecting telescope
definition: multiple mirror telescope
related: active optics
related: segmented optics
related: very large telescope

multiple star
type: Concept
change note: FVH: moved triple_star to NT (2007-OCT-1)
definition: multiple star
narrower: triple star
related: binary star
related: companion star
related: orbit
related: orbit determination

multi-slit spectrograph
type: Concept
broader: spectrograph
definition: multi-slit spectrograph
history note: FVH: new (2007-SEP-21)
related: integral field spectrograph
related: spectrograph slit
related: three-dimensional spectrum

muon
type: Concept
broader: lepton
definition: muon

nadir
type: Concept
broader: pole
definition: nadir
related: horizon coordinate system
related: zenith

naked singularity
type: Concept
broader: singularity
definition: naked singularity
related: black hole
related: quantum cosmology
related: space-time singularity
related: white hole

narrow band photometry
type: Concept
broader: CCD photometry
broader: photoelectric photometry
definition: narrow-band photometry
narrower: H alpha photometry
narrower: H beta photometry
related: broad band photometry
related: medium band photometry

Nasmyth focus
type: Concept
broader: focus
definition: Nasmyth focus
related: Cassegrain focus
related: Coude focus
related: Newtonian focus
related: prime focus
related: tertiary mirror

natural line broadening
type: Concept
broader: line broadening
definition: natural line broadening
related: natural line width
related: spectral line

natural line width
type: Concept
broader: line width
definition: natural line width
related: Doppler broadening
related: Stark broadening
related: Zeeman splitting
related: line broadening
related: natural line broadening
related: pressure broadening
related: spectral line

nautical almanac
type: Concept
broader: almanac
definition: nautical almanac
related: ephemeris

Navarro-Frenk-White profile
type: Concept
alternative label: NFW
alternative label: NFW profile
alternative label: NFW-profile
broader: mass distribution
definition: Navarro-Frenk-White mass-profile
history note: FVH: new (2007-OCT-5)
related: Burkert profile
related: exponential profile
related: isothermal sphere

N-body problem
type: Concept
alternative label: N body problem
alternative label: many body problem
alternative label: many-body problem
definition: N-body problem
related: N-body simulation
related: celestial mechanics
related: orbit
related: perturbation
related: stellar dynamics
related: three-body problem
related: two-body problem

N-body simulation
type: Concept
broader: numerical simulation
definition: N-body simulation
history note: FVH: new (2007-OCT-3)
related: N-body problem

nearby dwarf
type: Concept
broader: dwarf
broader: nearby star
definition: nearby dwarf star

nearby galaxy
type: Concept
broader: galaxy
definition: nearby galaxy
narrower: Local Group
narrower: Magellanic cloud
related: bright galaxy

nearby star
type: Concept
definition: nearby star
narrower: nearby dwarf
related: trigonometric parallax

near-Earth asteroid
type: Concept
alternative label: NEO
alternative label: near Earth asteroid
alternative label: near-Earth object
broader: asteroid
definition: near-Earth asteroid

near infrared radiation
type: Concept
broader: infrared radiation
definition: near infrared radiation
related: H magnitude
related: I magnitude
related: J magnitude
related: K magnitude
related: L magnitude
related: far infrared radiation
related: infrared photometry

near ultraviolet radiation
type: Concept
alternative label: NUV
broader: ultraviolet radiation
definition: near ultraviolet radiation
related: extreme ultraviolet radiation
related: far ultraviolet radiation

nebula
type: Concept
broader: interstellar matter
definition: nebula
narrower: bipolar nebula
narrower: bright nebula
narrower: compact nebula
narrower: dark nebula
narrower: dense cloud
narrower: diffuse nebula
narrower: dust nebula
narrower: emission nebula
narrower: filamentary nebula
narrower: gaseous nebula
narrower: planetary nebula
narrower: reflection nebula
narrower: ring nebula
related: Opik theory
related: forbidden line
related: forbidden transition
related: nebular filament
related: surface photometry
scope note: named nebula not included; not including galaxy

nebular filament
type: Concept
broader: interstellar matter
definition: nebular filament
related: filamentary nebula
related: nebula

negative H ion
type: Concept
alternative label: H minus ion
alternative label: H-
alternative label: H- ion
broader: hydrogen
definition: negative hydrogen ion
related: opacity
related: stellar atmosphere

neighborhood
type: Concept
definition: neighborhood
scope note: combine with other terms

neodymium
type: Concept
alternative label: Nd
broader: fundamental chemical element
broader: rare earth
definition: neodymium (atomic number 60)
history note: FVH: new (2007-OCT-25)

neon
type: Concept
alternative label: Ne
broader: fundamental chemical element
definition: neon (atomic number 10)
history note: FVH: new (2007-OCT-25)

Neptune
type: Concept
broader: Jovian planet
broader: planet
definition: Neptune
history note: FVH: new (2007-SEP-24)
related: Solar System

neptunium
type: Concept
alternative label: Np
broader: fundamental chemical element
definition: neptunium (atomic number 93)
history note: FVH: new (2007-OCT-25)

Neumann line
type: Concept
definition: Neumann line
related: emission line
related: emission spectrum
related: meteorite

neutral density filter
type: Concept
broader: filter
definition: neutral density filter
history note: FVH: new (2007-SEP-21)
related: attenuation

neutral gas
type: Concept
broader: gas
definition: neutral gas
narrower: H I
narrower: He I
related: H I region

neutrino
type: Concept
broader: elementary particle
broader: lepton
broader: particle
definition: neutrino
related: antineutrino
related: solar neutrino problem
related: supernova

neutron
type: Concept
broader: elementary particle
broader: fundamental particle
definition: neutron
related: alpha particle
related: nucleus atom

neutron star
type: Concept
broader: collapsed star
broader: compact object
broader: degenerate star
broader: relativistic star
broader: stellar object
definition: neutron star
narrower: HZ Herculis star
narrower: magnetar
related: Alfven surface
related: X-ray binary star
related: X-ray burst
related: X-ray pulsar
related: low-mass X-ray binary star
related: pulsar
related: quark
related: relativistic astrophysics
related: supernova remnant

Newtonian focus
type: Concept
broader: Newtonian telescope
broader: focus
definition: Newtonian focus
related: Cassegrain focus
related: Coude focus
related: Nasmyth focus

Newtonian gravitation
type: Concept
broader: gravitation
definition: Newtonian gravitation
related: MOdified Newtonian Dynamics
related: general theory of relativity
related: gravitational constant
related: gravitational force

Newtonian telescope
type: Concept
definition: Newtonian telescope
narrower: Newtonian focus

N galaxy
type: Concept
broader: compact galaxy
broader: galaxy
definition: N galaxy
related: Yerkes classification
related: galactic nucleus
related: giant radio galaxy

nickel
type: Concept
alternative label: Ni
broader: fundamental chemical element
definition: nickel (atomic number 28)
history note: FVH: new (2007-OCT-25)

night sky brightness
type: Concept
alternative label: night sky background
broader: sky brightness
definition: night sky brightness
related: Rayleigh
related: Rayleigh scattering
related: airglow
related: aurora
related: gegenschein
related: zodiacal light

night vision
type: Concept
definition: night vision
related: dark adaption

niobium
type: Concept
alternative label: Nb
broader: fundamental chemical element
definition: niobium (atomic number 41)
history note: FVH: new (2007-OCT-25)

nitrogen
type: Concept
alternative label: N
broader: fundamental chemical element
definition: nitrogen (atomic number 7)
history note: FVH: new (2007-OCT-25)
related: carbon nitrogen cycle

N magnitude
type: Concept
broader: apparent magnitude
definition: N magnitude
related: far infrared radiation
related: infrared photometry

nobelium
type: Concept
alternative label: No
broader: fundamental chemical element
definition: nobelium (atomic number 102)
history note: FVH: new (2007-OCT-25)

noctilucent cloud
type: Concept
broader: cloud
definition: noctilucent cloud
related: Earth atmosphere
related: luminescence
scope note: in Earth's atmosphere

node
type: Concept
alternative label: line of node
definition: node
narrower: ascending node
narrower: descending node
related: inclination
related: orbit
related: vibration

noise
type: Concept
change note: FVH: moved interference_noise to NT (2007-OCT-1)
definition: noise
narrower: background noise
narrower: cosmic noise
narrower: interference noise
narrower: read out noise
narrower: shot noise
narrower: sky noise
related: integration time
related: signal-to-noise ratio
scope note: combine with other terms

nomenclature
type: Concept
definition: nomenclature
related: catalog
related: classification

non-equilibrium flow
type: Concept
alternative label: nonequilibrium flow
broader: flow
definition: non-equilibrium flow
related: flow instability

non-LTE transfer
type: Concept
alternative label: nonLTE transfer
definition: non-LTE transfer
related: energy-transfer
related: local thermodynamic equilibrium
related: radiation mechanism

non-main sequence star
type: Concept
alternative label: nonmain_sequence star
definition: non-main_sequence star
narrower: evolved star
narrower: post-main sequence star
narrower: pre-main sequence star
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

non-radial pulsation
type: Concept
alternative label: nonradial pulsation
definition: non-radial pulsation
related: ZZ Ceti star
related: beta Cephei star
related: delta Scuti star
related: pulsating variable star
related: pulsation mode

non-thermal particle
type: Concept
alternative label: nonthermal particle
definition: non-thermal particle
related: non-thermal source

non-thermal radiation
type: Concept
alternative label: nonthermal radiation
definition: non-thermal radiation
related: non-thermal source

non-thermal source
type: Concept
alternative label: nonthermal source
broader: source
definition: non-thermal source
related: non-thermal particle
related: non-thermal radiation
related: synchrotron radiation

North Celestial Pole
type: Concept
alternative label: N.C.P.
alternative label: NCP
broader: celestial pole
definition: North Celestial Pole
related: South Celestial Pole

North Ecliptic Pole
type: Concept
alternative label: N.E.P.
alternative label: NEP
broader: ecliptic pole
definition: North Ecliptic Pole
related: South Ecliptic Pole

northern hemisphere
type: Concept
definition: northern hemisphere
related: southern hemisphere

North Galactic Pole
type: Concept
alternative label: N.G.P.
alternative label: NGP
broader: Galactic pole
definition: North Galactic Pole
related: South Galactic Pole

nova-like variable
type: Concept
broader: cataclysmic variable star
definition: nova-like variable
narrower: AM Canum Venaticorum star
narrower: UX Ursae Majoris star
narrower: VY Sculpturis star

nova
type: Concept
broader: eruptive binary star
broader: high-luminosity star
definition: nova
narrower: X-ray nova
narrower: classical nova
narrower: fast nova
narrower: recurrent nova
narrower: slow nova
narrower: symbiotic nova
related: mass-loss
related: optical outburst
related: pre-nova
related: progenitor
related: supernova

N star
type: Concept
broader: late-type star
definition: N star
related: spectral type
related: technetium star

nuclear astrophysics
type: Concept
definition: nuclear astrophysics
related: high-energy astrophysics
related: nuclear physics

nuclear fission
type: Concept
broader: fission
broader: nuclear reaction
definition: nuclear fission
related: cosmochronology
related: radioactivity

nuclear fusion
type: Concept
broader: fusion
broader: nuclear reaction
definition: nuclear fusion
narrower: carbon burning
narrower: helium burning
narrower: oxygen burning
narrower: silicon burning
related: carbon flash
related: carbon nitrogen cycle
related: e-process
related: helium flash
related: helium shell flash
related: hydrogen burning
related: proton-proton reaction
related: shell burning
related: stellar interior
related: supernova

nuclear physics
type: Concept
definition: nuclear physics
related: interaction
related: nuclear astrophysics
related: nuclear radiation
related: nuclear reaction
related: strong interaction
related: weak interaction

nuclear radiation
type: Concept
definition: nuclear radiation
narrower: alpha particle
narrower: electron
narrower: gamma-ray radiation
narrower: positron
related: Cerenkov radiation
related: nuclear physics

nuclear reaction
type: Concept
definition: nuclear reaction
narrower: nuclear fission
narrower: nuclear fusion
narrower: urca process
related: carbon burning
related: nuclear physics
related: nucleosynthesis
related: solar neutrino problem

nucleosynthesis
type: Concept
definition: nucleosynthesis
narrower: carbon burning
narrower: helium burning
narrower: hydrogen burning
narrower: oxygen burning
narrower: silicon burning
related: nuclear reaction
related: p process
related: r-process
related: s-process
related: stellar interior
related: supernova

nucleus atom
type: Concept
definition: nucleus [atom]
narrower: Bose-Einstein nucleus
narrower: Fermi-Dirac nucleus
related: neutron
related: proton

nucleus celestial object
type: Concept
definition: nucleus [celestial object]
narrower: compact nucleus
narrower: galactic nucleus
related: cD galaxy
related: comet
related: dirty snowball theory
scope note: combine with other terms

numerical analysis
type: Concept
broader: data processing
definition: numerical analysis
related: numerical integration
related: numerical method
related: numerical simulation

numerical integration
type: Concept
definition: numerical integration
related: numerical analysis
related: numerical method

numerical method
type: Concept
definition: numerical method
related: numerical analysis
related: numerical integration
related: numerical simulation

numerical simulation
type: Concept
definition: numerical simulation
narrower: N-body simulation
narrower: SPH simulation
related: computer model
related: model
related: numerical analysis
related: numerical method

nutation
type: Concept
definition: nutation
related: Earth rotation
related: Moon
related: equation of the equinox
related: polar motion
related: precession

O association
type: Concept
alternative label: O-association
broader: star association
definition: O association
related: O cluster
related: OB association

OB association
type: Concept
broader: star association
definition: OB association
related: O association
related: young star

objective grating
type: Concept
broader: diffraction grating
broader: transmission grating
definition: objective grating
related: echelle grating
related: reflection grating

objective
type: Concept
definition: objective [optics]
narrower: primary lens
narrower: primary mirror
related: optical telescope
scope note: primary optics of telescope

objective prism
type: Concept
broader: prism
definition: objective prism
related: Schmidt telescope

oblateness
type: Concept
definition: oblateness
related: elliptical galaxy
related: equatorial bulge
related: planet
related: rotation

oblique rotator
type: Concept
definition: oblique rotator
related: Ap star
related: magnetic star
related: spectrum variable star

obliquity of ecliptic
type: Concept
alternative label: obliquity
definition: obliquity of ecliptic
related: celestial equator
related: ecliptic
related: ecliptic plane
related: phase defect
related: precession

observational cosmology
type: Concept
definition: observational cosmology
related: Hubble law
related: color-redshift relation
related: cosmological distance scale
related: galaxy count
related: galaxy distribution
related: observation
related: radio source count
related: redshift
related: redshift distance relation

observation
type: Concept
definition: observation
narrower: CCD observation
narrower: optical observation
related: data acquisition
related: observational cosmology
related: observing technique
related: research
scope note: combine with other terms

observatory
type: Concept
definition: observatory
narrower: X-ray observatory
narrower: antarctic observatory
narrower: gamma-ray observatory
narrower: geophysical observatory
narrower: infrared observatory
narrower: optical observatory
narrower: radio observatory
narrower: space observatory
narrower: ultraviolet observatory
related: dome
related: planetarium
related: site protection
related: site testing
related: telescope
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

observing technique
type: Concept
alternative label: method of observation
definition: observing technique
narrower: astrometry
narrower: interferometry
narrower: photometry
narrower: polarimetry
narrower: radio astrometry
narrower: radio interferometry
narrower: spectrophotometry
narrower: spectroscopy
related: astronomical technique
related: data acquisition
related: data processing
related: observation
related: occultation
related: photography
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

OB star
type: Concept
broader: early-type star
broader: young star
definition: OB star
narrower: B star
narrower: O star
narrower: OB supergiant
related: runaway star
related: young star cluster

OB supergiant
type: Concept
broader: OB star
broader: early-type supergiant
definition: OB supergiant star
narrower: B supergiant
narrower: O supergiant

occultation
type: Concept
change note: FVH: added asteroid_occultation and lunar_occultation (2007-OCT-8)
definition: occultation
narrower: asteroid occultation
narrower: lunar occultation
narrower: radio occultation
related: Moon
related: angular diameter
related: binary star
related: diameter
related: eclipse
related: observing technique
related: planet
related: transit

occulting disk
type: Concept
definition: occulting disc UK
definition: occulting disk
related: separation
related: visual binary star

oceanography
type: Concept
definition: oceanography
related: ocean tide

ocean tide
type: Concept
broader: tide
definition: ocean tide
related: oceanography

O cluster
type: Concept
broader: open star cluster
definition: O-star cluster
related: B star
related: O association
related: O star

O dwarf
type: Concept
broader: O star
broader: dwarf
definition: O dwarf star

Oef star
type: Concept
broader: O star
broader: early-type emission star
definition: Oef star
related: Of star

Oe star
type: Concept
broader: O star
broader: early-type emission star
definition: Oe star

Of star
type: Concept
broader: O star
broader: early-type emission star
definition: Of star
related: Oef star

O giant
type: Concept
broader: O star
definition: O giant star

OH absorption
type: Concept
broader: interstellar absorption
definition: OH absorption
related: hydroxyl radical

OH cloud
type: Concept
broader: interstellar matter
definition: OH cloud
related: hydroxyl radical

OH emission
type: Concept
broader: emission spectrum
definition: OH emission
related: hydroxyl radical

OH IR star
type: Concept
alternative label: OH-IR star
broader: OH source
broader: giant
broader: infrared source
definition: OH/IR star
related: OH maser
related: hydroxyl radical
related: variable star

OH line
type: Concept
definition: OH line
related: hydroxyl radical

OH maser
type: Concept
broader: maser
definition: OH maser
related: OH IR star
related: SiO maser
related: hydroxyl radical
related: water maser
scope note: subtype not included

OH source
type: Concept
broader: radio source
definition: OH source
narrower: OH IR star
related: hydroxyl radical

old star
type: Concept
broader: evolved star
change note: FVH: added NT POPULATION_III_STARS (2007-SEP-21)
definition: old star
narrower: population II star
narrower: population III star
narrower: pre-Galactic star

O magnitude
type: Concept
broader: apparent magnitude
definition: O magnitude
related: far infrared radiation
related: infrared photometry

Omega baryon
type: Concept
alternative label: Omega(baryon)
broader: Omega parameter
definition: Omega(baryon), the cosmological baryon mass-density fraction
history note: FVH: new (2007-OCT-24)
related: baryon
related: mass density

Omega Lambda
type: Concept
alternative label: Omega(Lambda)
broader: Omega parameter
definition: Omega(Lambda), the cosmological vacuum energy density fraction
history note: FVH: new (2007-OCT-24)
related: cosmological constant
related: energy density

Omega mass
type: Concept
alternative label: Omega(mass)
broader: Omega parameter
definition: omega(mass), the cosmological matter density fraction
history note: FVH: new (2007-OCT-24)
related: mass density

Omega parameter
type: Concept
broader: cosmological parameter
definition: the cosmological density fraction parameter, Omega
history note: FVH: new (2007-SEP-21)
narrower: Omega baryon
narrower: Omega Lambda
narrower: Omega mass
related: cosmology
related: energy density
related: mass density

on-line system
type: Concept
alternative label: on line system
definition: on-line system
related: data center
related: data processing

Oort cloud
type: Concept
alternative label: Oort comet cloud
definition: Oort cloud
related: comet
related: trans-Neptunian object

Oort constant
type: Concept
broader: astronomical constant
definition: Oort constant
related: Galactic rotation
related: Galactic structure

Oort formulae
type: Concept
alternative label: Oort formulas
definition: Oort formulae
related: Galactic rotation
related: Galactic structure

Oosterhoff group
type: Concept
definition: Oosterhoff group
related: RR Lyrae star
related: globular star cluster
related: metal abundance

opacity
type: Concept
broader: optical property
definition: opacity
narrower: Kramers opacity
narrower: Rosseland opacity
related: absorption
related: atmosphere
related: negative H ion
related: optical depth
related: radiation
related: radiative transfer
related: transparency

open star cluster
type: Concept
broader: star cluster
definition: open star cluster
narrower: Galactic cluster
narrower: O cluster
narrower: young star cluster
related: blue straggler star
related: moving cluster parallax
related: population I star
related: radiant moving cluster
related: spiral arm
related: star association
related: turnoff point

open universe
type: Concept
broader: cosmology
definition: open universe
related: Big Bang theory
related: closed universe
related: steady-state theory

Opik theory
type: Concept
definition: Opik theory
related: nebula
related: supernova

opposition
type: Concept
definition: opposition
related: conjunction
related: quadrature
related: synodic period
related: syzygy
scope note: refers to planet position

optical aberration
type: Concept
alternative label: aberration
change note: FVH: renamed for more clarity (2007-OCT-3)
definition: aberration of optical image
narrower: astigmatism
narrower: chromatic aberration
narrower: comatic aberration
narrower: distortion
narrower: field curvature
narrower: spherical aberration
related: focus
related: lens
related: mirror
related: optical system
related: optics
related: telescope

optical burst
type: Concept
broader: burst
definition: optical burst
related: X-ray burst
related: burster
related: gamma-ray burst
related: radio burst
scope note: specifically from burster

optical component
type: Concept
definition: optical component
narrower: corrector plate
narrower: diffraction grating
narrower: field corrector
narrower: grism
narrower: interference filter
narrower: lens
narrower: mirror
narrower: optical fiber
narrower: optical filter
narrower: optical waveguide
narrower: optical window
scope note: not a complete list of terms

optical depth
type: Concept
alternative label: optical thickness
definition: optical depth
related: absorption coefficient
related: gas density
related: opacity

optical design
type: Concept
definition: optical design
related: optical instrument

optical double star
type: Concept
definition: apparent optical double star
related: angular separation
scope note: use only for pair in chance alignment; refer also to visual binary star

optical fiber
type: Concept
alternative label: glass fiber
broader: optical component
broader: optical waveguide
definition: optical fiber
related: fiber optics
related: glass
related: multi-fiber spectrograph
related: optical instrument

optical film
type: Concept
alternative label: film [optical]
definition: optical film
narrower: antireflection coating
narrower: thin film
related: dichroic mirror
related: interference filter
related: light interference

optical filter
type: Concept
alternative label: color filter
broader: filter
broader: optical component
definition: optical filter
narrower: interference filter
narrower: iodine cell
narrower: photographic filter
related: dichroic mirror
related: light interference
related: optical window
related: photometry
related: ultraviolet filter

optical flare
type: Concept
broader: flare
definition: optical flare
related: flare star
related: prominence

optical glass
type: Concept
broader: glass
broader: optical material
definition: optical glass
related: optical window

optical identification
type: Concept
alternative label: optical counterparts
definition: optical identification
related: X-ray identification
related: X-ray source
related: gamma-ray source
related: radio source

optical instrument
type: Concept
alternative label: optical equipment
definition: optical instrument
narrower: camera
narrower: coronagraph
narrower: monochromator
narrower: optical scanners
narrower: photometer
narrower: polarimeter
narrower: seeing monitor
narrower: spectrograph
narrower: telescope
related: Hartmann test
related: collimator
related: field corrector
related: lens
related: mirror
related: modulation transfer function
related: optical design
related: optical fiber
related: optical material
related: optical system
related: optical testing
related: optical transfer function
related: prism
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

optical interferometer
type: Concept
alternative label: stellar interferometer
broader: interferometer
definition: optical interferometer
narrower: Michelson interferometer
narrower: intensity interferometer
related: long baseline interferometer

optical interferometry
type: Concept
alternative label: light interferometry
alternative label: stellar interferometry
broader: interferometry
definition: optical interferometry
related: Michelson interferometry
related: interference fringe
related: interference wave
related: light interference
related: long baseline interferometry

optical material
type: Concept
definition: optical material
narrower: glass
narrower: optical glass
related: lens
related: mirror
related: optical instrument

optical observation
type: Concept
broader: observation
definition: optical observation
related: optical observatory

optical observatory
type: Concept
broader: observatory
definition: optical observatory
narrower: Hubble Space Telescope
related: optical observation
related: optical telescope
related: seeing monitor

optical outburst
type: Concept
broader: outburst
definition: optical outburst
related: cataclysmic variable star
related: flare star
related: nova
related: supernova
scope note: not from burster

optical pathlength
type: Concept
definition: optical pathlength
related: refractive index

optical position
type: Concept
definition: optical position
related: astrometry

optical property
type: Concept
broader: property
definition: optical property
narrower: albedo
narrower: brightness
narrower: color
narrower: opacity
narrower: refractive index
related: brightness temperature
related: darkness
related: isotropy
related: light polarization
related: optics
scope note: not a complete list of terms

optical pulsar
type: Concept
broader: pulsar
definition: optical pulsar
related: radio pulsar

optical radar
type: Concept
broader: radar
definition: optical radar
related: laser
related: laser ranging
related: lunar laser ranging
related: satellite laser ranging

optical scanners
type: Concept
broader: optical instrument
definition: optical scanners
related: spectrophotometry

optical spectrograph
type: Concept
alternative label: optical spectrometer
broader: spectrograph
definition: optical spectrograph

optical spectroscopy
type: Concept
broader: spectroscopy
definition: optical spectroscopy

optical surface
type: Concept
change note: FVH: renamed from optical_surface (2007-OCT-2)
definition: optical surface
related: aluminum coating
related: antireflection coating
related: figuring
related: lens
related: mirror
related: polishing
related: silver coating
related: thin film

optical system
type: Concept
definition: optical system
narrower: catadioptric system
narrower: catoptric system
narrower: dioptric system
related: aperture
related: chromatic aberration
related: comatic aberration
related: distortion
related: field curvature
related: optical aberration
related: optical instrument

optical telescope
type: Concept
broader: telescope
definition: optical telescope
narrower: automatic patrol telescope
narrower: multiple mirror telescope
narrower: reflecting telescope
narrower: refracting telescope
narrower: very large telescope
related: catadioptric system
related: catoptric system
related: dioptric system
related: eyepiece
related: objective
related: optical observatory
related: secondary mirror
related: tertiary mirror

optical testing
type: Concept
definition: optical testing
related: figuring
related: modulation transfer function
related: optical instrument
related: optical transfer function

optical transfer function
type: Concept
alternative label: OTF
broader: transfer function
definition: optical transfer function
related: modulation transfer function
related: optical instrument
related: optical testing

optical transmission window
type: Concept
broader: atmospheric window
change note: FVH: renamed to avoid confusion with optics (2007-NOV-2)
definition: optical transmission window through the atmosphere
related: infrared transmission window
related: radio transmission window
scope note: low absorption in atmosphere

optical waveguide
type: Concept
broader: optical component
broader: waveguide
definition: optical waveguide
narrower: optical fiber

optical window
type: Concept
broader: optical component
definition: optical window [optics]
related: optical filter
related: optical glass

optics
type: Concept
definition: optics
narrower: active optics
narrower: adaptive optics
narrower: astronomical optics
narrower: fiber optics
related: adjustment
related: angular resolution
related: collimation
related: optical aberration
related: optical property
related: refractive index
related: resolution
related: transmission
scope note: combine with other terms

orbital anomaly
type: Concept
alternative label: apparent anomaly
broader: orbital element
definition: orbital_anomaly
narrower: eccentric anomaly
narrower: mean anomaly
narrower: real anomaly
narrower: true anomaly
related: anomalistic month
related: anomalistic year

orbital element
type: Concept
change note: FVH: removed element_of_orbit (2007-SEP-24)
definition: orbital element
narrower: apsis
narrower: center of mass
narrower: eccentricity
narrower: inclination
narrower: orbital anomaly
narrower: osculatory element
narrower: period
narrower: position angle
narrower: semimajor axis
related: acceleration
related: celestial mechanics
related: orbit
related: regression of node
scope note: see also orbit

orbital evolution
type: Concept
definition: orbital evolution
related: celestial mechanics

orbital motion
type: Concept
broader: motion
definition: orbital motion
related: celestial mechanics
related: circular orbit
related: orbital velocity
related: visual binary star

orbital theory
type: Concept
definition: orbital theory
related: celestial mechanics

orbital velocity
type: Concept
broader: velocity
definition: orbital velocity
related: angular velocity
related: escape velocity
related: orbit
related: orbital motion
related: tangential velocity

orbit determination
type: Concept
definition: orbit determination
related: binary star
related: multiple star
related: planet

orbit
type: Concept
definition: orbit
narrower: Keplerian orbit
narrower: elliptical orbit
narrower: geocentric orbit
narrower: heliocentric orbit
narrower: hyperbolic orbit
narrower: osculating orbit
narrower: parabolic orbit
narrower: periodic orbit
narrower: polar orbit
related: Local Standard of Rest
related: N-body problem
related: Roche limit
related: Schwarzschild metric
related: acceleration
related: apsidal motion
related: apsis
related: binary star
related: celestial mechanics
related: high-velocity star
related: motion
related: multiple star
related: node
related: orbital element
related: orbital velocity
related: parabolic velocity
related: period
related: perturbation
related: perturbation theory
related: planet
related: position angle
related: synchronous rotation
related: three-body problem
related: trajectory
scope note: see also orbital element

organic matter
type: Concept
definition: organic matter
narrower: organic molecule

organic molecule
type: Concept
broader: molecule
broader: organic matter
definition: organic molecule
related: interstellar molecule
related: molecular spectrum

orientation
type: Concept
definition: orientation
related: adjustment
related: alignment optics
related: collimation
related: position angle

origin
type: Concept
definition: origin
related: Solar System
related: chemical element
related: element formation
related: galaxy
related: life
related: planet
scope note: combine with other terms

orion population star
type: Concept
definition: orion population star
related: early-type star
related: pre-main sequence star

orrery
type: Concept
broader: model
definition: orrery
related: motion
related: planetarium

orthohydrogen
type: Concept
broader: molecular hydrogen
definition: orthohydrogen
related: parahydrogen

orthoscopic eyepiece
type: Concept
broader: eyepiece
definition: orthoscopic eyepiece

oscillating universe
type: Concept
broader: cosmology
definition: oscillating universe
related: Friedmann universe

oscillation
type: Concept
definition: oscillation
related: amplitude
related: decay oscillation
related: e-folding time
related: pendulum
related: wave
scope note: combine with other terms

oscillator strength
type: Concept
alternative label: f value
alternative label: f-value
definition: oscillator strength
related: g value
related: gf value
related: line formation
related: line width
related: transition probability

osculating orbit
type: Concept
broader: orbit
definition: osculating orbit

osculatory element
type: Concept
broader: orbital element
definition: osculatory element
related: celestial mechanics
related: perturbation

osmium
type: Concept
alternative label: Os
broader: fundamental chemical element
definition: osmium (atomic number 76)
history note: FVH: new (2007-OCT-25)

O star
type: Concept
broader: OB star
broader: early-type star
broader: young star
definition: O star
narrower: O dwarf
narrower: O giant
narrower: O subdwarf
narrower: O supergiant
narrower: Oe star
narrower: Oef star
narrower: Of star
related: O cluster
related: Wolf-Rayet star
related: early-type variable star
related: spectral type

O subdwarf
type: Concept
broader: O star
broader: subdwarf
definition: O subdwarf star

O supergiant
type: Concept
broader: O star
broader: OB supergiant
broader: early-type supergiant
broader: supergiant
definition: O supergiant star

outburst
type: Concept
broader: burst
broader: flare
definition: outburst
narrower: optical outburst
related: high-state
related: low-state

outer planet
type: Concept
broader: planet
definition: outer planet
narrower: Jovian planet
related: inner planet

outgassing
type: Concept
definition: outgassing
related: cryogenics
related: vacuum technique

overabundance
type: Concept
broader: abundance
definition: overabundance
history note: ES: new (2007-OCT-8)
related: underabundance

overtone frequency
type: Concept
alternative label: harmonic overtones
alternative label: overtones
definition: overtone frequency
related: Fourier analysis
related: fundamental frequency
related: harmonic frequency
related: multi-periodic variable star
related: overtone mode
scope note: see sn for overtone mode; also see harmonic frequency

overtone mode
type: Concept
alternative label: overtones
broader: pulsation mode
definition: overtone mode
related: fundamental mode
related: multi-periodic variable star
related: overtone frequency
related: pulsating variable star
scope note: of pulsation frequency, not Fourier component of non-sinusoidal variation

oxygen burning
type: Concept
broader: nuclear fusion
broader: nucleosynthesis
definition: oxygen burning
related: carbon burning
related: helium burning
related: hydrogen burning
related: oxygen
related: stellar interior

oxygen
type: Concept
alternative label: O
broader: fundamental chemical element
definition: oxygen (atomic number 8)
history note: FVH: new (2007-OCT-25)
related: oxygen burning
related: titanium oxide

ozone layer
type: Concept
definition: ozone layer
related: Earth atmosphere

pair annihilation
type: Concept
definition: pair annihilation
related: electron
related: gamma-ray radiation
related: positron

pair production
type: Concept
broader: particle production
definition: pair production
related: electron
related: gamma-ray radiation
related: positron

paleomagnetism
type: Concept
definition: paleomagnetism
related: continental drift
related: geomagnetism
related: magnetic field

palladium
type: Concept
alternative label: Pd
broader: fundamental chemical element
definition: palladium (atomic number 46)
history note: FVH: new (2007-OCT-25)

parabolic antenna
type: Concept
alternative label: parabolic antennas
broader: antenna
broader: directional antenna
definition: parabolic antenna
related: Cassegrain focus

parabolic mirror
type: Concept
definition: parabolic mirror
related: parabolic reflector
scope note: see parabolic reflector

parabolic orbit
type: Concept
broader: orbit
definition: parabolic orbit
related: circular orbit
related: comet
related: elliptical orbit
related: hyperbolic orbit

parabolic reflector
type: Concept
definition: parabolic reflector
related: dish antenna
related: parabolic mirror
related: radar telescope
related: radio telescope
related: reflecting telescope

parabolic velocity
type: Concept
broader: velocity
definition: parabolic velocity
related: escape velocity
related: orbit

parahydrogen
type: Concept
broader: molecular hydrogen
definition: parahydrogen
related: orthohydrogen

parallax
type: Concept
definition: parallax
narrower: annual parallax
narrower: diurnal parallax
narrower: dynamical parallax
narrower: kinematic parallax
narrower: moving cluster parallax
narrower: photometric parallax
narrower: secular parallax
narrower: statistical parallax
narrower: trigonometric parallax
related: Astronomical Unit
related: astrometry
related: distance
related: distance modulus

parallel computer
type: Concept
broader: computer
definition: parallel computer
history note: FVH: new (2007-SEP-21)

parametric amplifier
type: Concept
broader: amplifier
definition: parametric amplifier

parsec
type: Concept
alternative label: parallax second
definition: parsec
related: Astronomical Unit
related: distance
related: distance scale
related: light year

partial eclipse
type: Concept
broader: eclipse
definition: partial eclipse
related: eclipsing binary star
related: total eclipse

particle acceleration
type: Concept
definition: particle acceleration
related: elementary particle

particle accretion
type: Concept
definition: particle accretion
related: accretion

particle beam
type: Concept
definition: particle beam
related: high-energy astrophysics

particle creation
type: Concept
definition: particle creation
related: elementary particle

particle escape
type: Concept
definition: particle escape
related: elementary particle

particle interaction
type: Concept
definition: particle interaction
related: elementary particle

particle
type: Concept
definition: particle
narrower: alpha particle
narrower: boson
narrower: electron
narrower: elementary particle
narrower: fundamental particle
narrower: ion
narrower: lepton
narrower: neutrino
narrower: plasma
narrower: positron
narrower: proton
narrower: relativistic particle
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

particle production
type: Concept
definition: particle production
narrower: pair production
related: elementary particle

particle propagation
type: Concept
definition: particle propagation

Paschen-Back effect
type: Concept
definition: Paschen-Back effect
related: Zeeman splitting
related: magnetic field

Paschen series
type: Concept
alternative label: Paschen line
broader: hydrogen spectrum
definition: Paschen series
related: Balmer series
related: Brackett series
related: Lyman series
related: Pfund series

past light cone
type: Concept
broader: light cone
definition: past light cone
related: future light cone

Paul trap
type: Concept
definition: Paul trap
related: electric field
related: ion
related: radio frequency

p branch
type: Concept
broader: molecular spectrum
definition: p-branch

P Cygni line profile
type: Concept
broader: line profile
definition: P Cygni line profile
related: S Doradus star
related: emission line star
related: mass-loss
related: shell star
related: symbiotic star

peculiar galaxy
type: Concept
broader: galaxy
broader: peculiar object
definition: peculiar galaxy
narrower: Ep galaxy
narrower: Seyfert galaxy
narrower: compact galaxy
narrower: dwarf galaxy
narrower: emission line galaxy
narrower: interacting galaxy
narrower: ring galaxy
related: Markarian galaxy

peculiar giant
type: Concept
broader: giant
broader: peculiar star
definition: peculiar giant star

peculiar motion
type: Concept
definition: peculiar motion
related: Local Standard of Rest
related: peculiar velocity
related: proper motion
related: radial velocity
related: stellar motion

peculiar object
type: Concept
definition: peculiar object
narrower: peculiar galaxy
narrower: peculiar star
scope note: combine with other terms

peculiar star
type: Concept
broader: peculiar object
definition: peculiar star
narrower: Ap star
narrower: Bp star
narrower: heavy metal star
narrower: holmium star
narrower: magnetic star
narrower: peculiar giant
narrower: peculiar variable star
related: abnormal spectrum
related: abundance
related: chemical composition
related: emission line star
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

peculiar variable star
type: Concept
broader: peculiar star
broader: variable star
definition: peculiar variable star

peculiar velocity
type: Concept
broader: velocity
definition: peculiar velocity
related: Local Standard of Rest
related: peculiar motion
related: radial velocity
related: stellar motion

pencil beam
type: Concept
definition: pencil beam
related: Mills cross antenna
related: radio interferometer

pendulum
type: Concept
broader: timing equipment
definition: pendulum
related: geodesy
related: gravity
related: oscillation

Penrose process
type: Concept
definition: Penrose process
related: black hole

penumbral filament
type: Concept
definition: penumbral filament
related: penumbra

penumbra
type: Concept
alternative label: penumbras
definition: penumbra
related: Wilson effect
related: eclipse
related: lunar eclipse
related: penumbral filament
related: solar eclipse
related: sunspot
related: umbra

periapsis
type: Concept
definition: periapsis
related: periastron
related: perihelion

periastron
type: Concept
broader: apsis
definition: periastron
related: apastron
related: periapsis

pericenter
type: Concept
definition: pericenter
related: center of mass

perigee
type: Concept
broader: apsis
definition: perigee
related: Earth
related: Moon
related: apogee

perihelion
type: Concept
broader: apsis
definition: perihelion
related: Earth orbit
related: aphelion
related: periapsis
related: planet

period-age relation
type: Concept
alternative label: period age relation
broader: statistical relation
definition: period-age relation
related: Cepheid
related: period-color relation
related: period-density relation
related: period-luminosity-color relation
related: period-luminosity relation
related: period-mass relation
related: period-radius relation
related: period-spectrum relation

period change
type: Concept
alternative label: period variation
definition: period change
related: binary star
related: pulsating variable star

period-color relation
type: Concept
alternative label: period color relation
broader: statistical relation
definition: period-color relation
related: Cepheid
related: period-age relation
related: period-density relation
related: period-luminosity-color relation
related: period-luminosity relation
related: period-mass relation
related: period-radius relation
related: period-spectrum relation
related: pulsating variable star
related: radius-luminosity relation

period-density relation
type: Concept
alternative label: period density relation
broader: statistical relation
definition: period-density relation
related: period-age relation
related: period-color relation
related: period-luminosity-color relation
related: period-luminosity relation
related: period-mass relation
related: period-radius relation
related: period-spectrum relation
related: pulsating variable star
related: radius-luminosity relation

period determination
type: Concept
definition: period determination
related: binary star
related: variable star
related: waveform analysis

periodic comet
type: Concept
broader: comet
definition: periodic comet

periodic orbit
type: Concept
broader: orbit
definition: periodic orbit
narrower: elliptical orbit

periodic variable star
type: Concept
broader: pulsating variable star
broader: rotating star
definition: periodic variable star
history note: FVH: new (2007-OCT-8)
narrower: multi-periodic variable star

period-luminosity-color relation
type: Concept
alternative label: PLC relation
alternative label: period luminosity color relation
broader: statistical relation
definition: period-luminosity-color relation
related: Cepheid
related: period-age relation
related: period-color relation
related: period-density relation
related: period-luminosity relation
related: period-mass relation
related: period-radius relation
related: period-spectrum relation
related: pulsating variable star
related: radius-luminosity relation

period-luminosity relation
type: Concept
alternative label: PL relation
alternative label: period luminosity relation
broader: statistical relation
definition: period-luminosity relation
related: Cepheid
related: period-age relation
related: period-color relation
related: period-density relation
related: period-luminosity-color relation
related: period-mass relation
related: period-radius relation
related: period-spectrum relation
related: pulsating variable star
related: radius-luminosity relation

period-mass relation
type: Concept
alternative label: period mass relation
broader: statistical relation
definition: period-mass relation
related: period-age relation
related: period-color relation
related: period-density relation
related: period-luminosity-color relation
related: period-luminosity relation
related: period-radius relation
related: period-spectrum relation
related: pulsating variable star
related: radius-luminosity relation

period
type: Concept
broader: orbital element
broader: photometric element
definition: period
related: binary star
related: cycle
related: light curve
related: orbit
related: phase wave
related: planet
related: pulsating variable star
related: pulsation mode
related: rotation
related: variable star
related: velocity curve

period-radius relation
type: Concept
alternative label: period radius relation
broader: statistical relation
definition: period-radius relation
related: Cepheid
related: period-age relation
related: period-color relation
related: period-density relation
related: period-luminosity-color relation
related: period-luminosity relation
related: period-mass relation
related: period-spectrum relation
related: pulsating variable star
related: radius-luminosity relation

period-spectrum relation
type: Concept
alternative label: period spectrum relation
broader: statistical relation
definition: period-spectrum relation
related: Cepheid
related: period-age relation
related: period-color relation
related: period-density relation
related: period-luminosity-color relation
related: period-luminosity relation
related: period-mass relation
related: period-radius relation
related: pulsating variable star
related: radius-luminosity relation

peripheral
type: Concept
definition: peripheral
related: computer
related: instrument
scope note: combine with other terms

perturbation
type: Concept
definition: perturbation
related: N-body problem
related: celestial mechanics
related: orbit
related: osculatory element
related: perturbation theory
related: three-body problem

perturbation theory
type: Concept
definition: perturbation theory
related: celestial mechanics
related: gravitation
related: orbit
related: perturbation

petrology
type: Concept
broader: geology
definition: petrology
related: planet
related: surface of celestial body

Pfund series
type: Concept
broader: hydrogen spectrum
broader: infrared radiation
definition: Pfund series
related: Balmer series
related: Brackett series
related: Lyman series
related: Paschen series

PG1159 star
type: Concept
alternative label: GW Virginis star
alternative label: PG1159-35 star
broader: DO star
broader: multi-periodic variable star
definition: PG1159 star
history note: ES: new (2007-OCT-8)

phase angle
type: Concept
definition: phase angle
related: Moon
related: lunar phase
related: planet

phased array
type: Concept
broader: array
definition: phased array
related: phase wave
related: radio interferometer

phase defect
type: Concept
definition: phase defect
related: Moon
related: lunar phase
related: obliquity of ecliptic

phase difference
type: Concept
definition: phase difference
related: phase wave

phase effect
type: Concept
definition: phase effect
related: lunar phase

phase error
type: Concept
definition: phase error
related: phase wave

phase function
type: Concept
definition: phase function
related: phase wave
related: radiation scattering

phase rotator
type: Concept
definition: phase rotator
related: phase wave
related: radio telescope

phase sensitive detector
type: Concept
definition: phase sensitive detector
related: phase switching interferometer
related: phase wave
related: receiver

phase shift
type: Concept
alternative label: phase-shift
definition: phase shift
related: light curve
related: phase wave
related: variable star
related: velocity curve

phase space
type: Concept
definition: phase space
related: phase wave
related: velocity space

phase switching interferometer
type: Concept
broader: interferometer
definition: phase switching interferometer
related: phase sensitive detector
related: phase wave

phase switching
type: Concept
definition: phase switching
related: phase wave
related: radio telescope
related: receiver

phase wave
type: Concept
definition: phase of a repeating wave
related: binary star
related: light curve
related: period
related: phase difference
related: phase error
related: phase function
related: phase rotator
related: phase sensitive detector
related: phase shift
related: phase space
related: phase switching
related: phase switching interferometer
related: phased array
related: variable star
related: velocity curve

Phillips band
type: Concept
broader: infrared radiation
broader: molecular band
broader: molecular spectrum
definition: Phillips band

phosphorescence
type: Concept
definition: phosphorescence
related: image tube
related: phosphorescent scintillation
related: phosphorus
related: scintillation counter

phosphorescent scintillation
type: Concept
broader: scintillation
definition: phosphorescent scintillation
related: cosmic ray shower
related: image tube
related: phosphorescence
related: scintillation counter

phosphorus
type: Concept
alternative label: P
broader: fundamental chemical element
definition: phosphorus (atomic number 15)
history note: FVH: new (2007-OCT-25)
related: phosphorescence

photocathode
type: Concept
broader: cathode
broader: electrode
definition: photocathode
related: image tube
related: photomultiplier tube

photochemistry
type: Concept
definition: photochemistry
related: photographic developer
related: photographic material
related: photographic processing

photoconductive cell
type: Concept
definition: photoconductive cell
related: photomultiplier tube

photodiode
type: Concept
broader: photoelectronic device
definition: photodiode
narrower: avalanche photodiode
related: photometry

photodissociation
type: Concept
definition: photodissociation
related: absorption

photoelectric instrument
type: Concept
definition: photoelectric instrument
narrower: image tube
narrower: photomultiplier tube

photoelectric magnitude
type: Concept
broader: apparent magnitude
definition: photoelectric magnitude
related: photographic magnitude
related: photovisual magnitude

photoelectric photometer
type: Concept
broader: photometer
definition: photoelectric photometer

photoelectric photometry
type: Concept
broader: photometry
definition: photoelectric photometry
narrower: broad band photometry
narrower: medium band photometry
narrower: narrow band photometry
related: CCD photometry
related: photographic photometry

photoelectronic device
type: Concept
definition: photoelectronic device
narrower: avalanche photodiode
narrower: charge-coupled device
narrower: charge-injection device
narrower: charge-transfer device
narrower: image tube
narrower: photodiode
narrower: photomultiplier tube
narrower: television detector

photogrammetry
type: Concept
definition: photogrammetry
related: map
related: photograph
related: photography

photographic astrometry
type: Concept
broader: astrometry
definition: photographic astrometry
related: proper motion

photographic developer
type: Concept
definition: photographic developer
related: photochemistry
related: photograph
related: photographic processing

photographic emulsion
type: Concept
broader: detector
broader: photographic material
definition: photographic emulsion
related: halation
related: photograph
related: photographic film
related: photographic plate
related: photography
related: quantum efficiency
related: turbidity

photographic film
type: Concept
alternative label: film [photographic]
broader: photographic material
definition: photographic film
related: photograph
related: photographic emulsion
related: photography

photographic filter
type: Concept
broader: optical filter
definition: photographic filter

photographic instrument
type: Concept
definition: photographic instrument
narrower: Schmidt camera
narrower: Schmidt telescope
narrower: camera

photographic magnitude
type: Concept
broader: apparent magnitude
definition: photographic magnitude
related: photoelectric magnitude
related: photovisual magnitude

photographic material
type: Concept
definition: photographic material
narrower: photographic emulsion
narrower: photographic film
narrower: photographic plate
related: photochemistry
related: photograph

photographic photometry
type: Concept
broader: photometry
definition: photographic photometry
narrower: broad band photometry
related: CCD photometry
related: photoelectric photometry

photographic plate
type: Concept
broader: photographic material
definition: photographic plate
related: photograph
related: photographic emulsion
related: photography
related: reseaux

photographic processing
type: Concept
definition: photographic processing
related: darkroom
related: photochemistry
related: photographic developer
related: photography
related: unsharp masking

photograph
type: Concept
broader: image
definition: photograph
related: camera
related: microdensitometer
related: photogrammetry
related: photographic developer
related: photographic emulsion
related: photographic film
related: photographic material
related: photographic plate

photography
type: Concept
alternative label: astrophotography
definition: photography
narrower: all-sky photography
narrower: color photography
narrower: false color photography
narrower: spectrography
narrower: streak photography
narrower: ultraviolet photography
related: HD curve
related: astronomical technique
related: camera
related: darkroom
related: edge effect
related: image
related: microphotometer
related: observing technique
related: photogrammetry
related: photographic emulsion
related: photographic film
related: photographic plate
related: photographic processing
related: unsharp masking

photoheliograph
type: Concept
definition: photoheliograph
related: spectroheliograph

photoionization
type: Concept
alternative label: photoionisation UK
broader: ionization
definition: photoionization
related: absorption
related: aurora
related: electron
related: recombination

photoluminescence
type: Concept
broader: light emission
definition: photoluminescence
narrower: X-ray fluorescence
related: fluorescence

photometer
type: Concept
broader: optical instrument
broader: telescope instrument
definition: photometer
narrower: high-speed photometer
narrower: photoelectric photometer
narrower: spectrophotometer
related: CCD detector
related: bolometer
related: infrared detector
related: photometry
related: photomultiplier tube
related: polarimeter
related: radiometer
related: ultraviolet detector

photometric element
type: Concept
definition: photometric element
narrower: light curve
narrower: maximum
narrower: minimum
narrower: period
related: eclipsing binary star

photometric parallax
type: Concept
broader: parallax
definition: photometric parallax
related: photometry

photometric standard star
type: Concept
broader: standard star
definition: photometric standard star
related: photometry
related: standard candle

photometric system
type: Concept
definition: photometric system
narrower: Bessel photometry
narrower: Cape photometry
narrower: DDO photometry
narrower: Geneva photometry
narrower: Gunn photometry
narrower: HST photometry
narrower: Johnson photometry
narrower: Kron-Cousins photometry
narrower: Sloan photometry
narrower: Stromgren photometry
narrower: Walraven photometry
narrower: rgb photometry
related: apparent magnitude
related: photometry

photometry
type: Concept
alternative label: filter photometry
broader: astronomical technique
broader: observing technique
definition: photometry
narrower: CCD photometry
narrower: infrared photometry
narrower: multi-color photometry
narrower: photoelectric photometry
narrower: photographic photometry
narrower: surface photometry
narrower: ultraviolet photometry
related: Purkinje effect
related: apparent magnitude
related: automatic patrol telescope
related: avalanche photodiode
related: color
related: color equation
related: color excess
related: color index
related: color-luminosity relation
related: color-magnitude relation
related: drift scan
related: e region
related: effective temperature
related: f region
related: interference filter
related: intrinsic color
related: magnitude
related: optical filter
related: photodiode
related: photometer
related: photometric parallax
related: photometric standard star
related: photometric system
related: polarimetry
related: spectrophotometry
related: standard candle
related: two-color diagram
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

photomultiplier tube
type: Concept
alternative label: photocell
alternative label: photoelectric cell
broader: detector
broader: photoelectric instrument
broader: photoelectronic device
definition: photomultiplier tube
related: amplifier
related: cathode
related: electrode
related: photocathode
related: photoconductive cell
related: photometer
related: quadrant detector
related: quantum efficiency
related: scintillation counter

photon counting system
type: Concept
definition: photon counting system
related: counter

photon
type: Concept
broader: boson
broader: elementary particle
definition: photon
related: electromagnetic radiation
related: inverse Compton effect
related: inverse Compton scattering
related: meson
related: quanta
related: radiation
related: radiation pressure
related: radiation scattering
related: radiative recombination

photosphere
type: Concept
alternative label: reversing layer
definition: photosphere
related: Sun
related: chromosphere
related: continuum radiation
related: facula
related: granulation
related: granule
related: solar surface
related: surface brightness
related: surface of celestial body
scope note: ALT reversing_layer seems old-fashioned (IAU)!

photovisual magnitude
type: Concept
broader: apparent magnitude
definition: photovisual magnitude
related: V magnitude
related: photoelectric magnitude
related: photographic magnitude
related: visual magnitude

photovoltaic cell
type: Concept
broader: semiconductor device
definition: photovoltaic cell

physical constant
type: Concept
alternative label: fundamental constant
broader: constant
change note: FVH: renamed (see constant) (2007-OCT-11)
definition: physical constant
narrower: Planck constant
narrower: gravitational constant
narrower: velocity of light
related: astronomical constant

pion
type: Concept
broader: boson
broader: elementary particle
definition: pion

pitch angle
type: Concept
definition: pitch angle
related: Galactic structure
related: galaxy structure
related: spiral arm
related: spiral galaxy

pixel
type: Concept
alternative label: picture element
alternative label: voxel
definition: pixel
related: detector
related: resolution
related: two-dimensional detector

plage
type: Concept
definition: flocculi
definition: plage
definition: solar plage
related: chromosphere
related: facula
related: sunspot

Planck black body formula
type: Concept
definition: Planck black body formula
related: Planck constant
related: electromagnetic radiation
related: radiation

Planck constant
type: Concept
broader: physical constant
definition: Planck's constant h
related: Planck black body formula

plane polarization
type: Concept
alternative label: linear polarization
alternative label: plane polarisation UK
broader: light polarization
change note: FVH: added ALT linear polarization (2007-SEP-21)
definition: plane polarization
related: circular polarization
related: half-wave plate

planetarium
type: Concept
definition: planetarium
related: motion
related: observatory
related: orrery

planetar
type: Concept
broader: stellar object
definition: planetar
history note: FVH: new (2007-OCT-12)
related: brown dwarf
related: planet

planetary alignment
type: Concept
definition: alignment of planet, etc.
related: Solar System
related: celestial mechanics
related: planet

planetary microlensing
type: Concept
broader: gravitational microlensing
definition: microlensing of exoplanet
history note: FVH: new (2007-OCT-8)
related: planet

planetary nebula
type: Concept
broader: emission nebula
broader: evolved star
broader: nebula
definition: planetary nebula
related: Harman-Seaton sequence
related: ansa
related: central star
related: emission line star
related: exciting star
related: mass-loss
related: ring nebula

planetary
type: Concept
definition: planetary
scope note: see sn for planet

planetary ring
type: Concept
broader: ring
definition: planetary ring
related: Roche limit
related: planet
related: resonance gap
related: ring division
related: shepherd satellite

planetary system
type: Concept
definition: planetary system
narrower: Solar System

planetary theory
type: Concept
definition: planetary theory
related: Solar System
related: celestial mechanics

planetesimal
type: Concept
definition: planetesimal
related: Solar System
related: asteroid
related: planet
related: protoplanet
related: satellite

planetology
type: Concept
definition: planetology
related: geology

planet
type: Concept
broader: rotating body
change note: FVH: added lots of planet, RT DWARF_PLANETS (2007-SEP-24)
definition: planet
narrower: Earth
narrower: Jupiter
narrower: Mars
narrower: Mercury
narrower: Neptune
narrower: Saturn
narrower: Uranus
narrower: Venus
narrower: extrasolar planet
narrower: giant planet
narrower: hypothetical planet
narrower: inner planet
narrower: outer planet
related: Bodes law
related: Roche limit
related: Solar System
related: aeronomy
related: aphelion
related: astrology
related: atmosphere
related: boundary layer
related: center of mass
related: collision
related: composition
related: core
related: crater
related: crust
related: dust storm
related: dwarf planet
related: equatorial bulge
related: evolution
related: exosphere
related: galilean satellite
related: geology
related: geomagnetism
related: greenhouse effect
related: interior
related: lithosphere
related: mantle
related: map
related: mean equinox
related: oblateness
related: occultation
related: orbit
related: orbit determination
related: origin
related: perihelion
related: period
related: petrology
related: phase angle
related: planetar
related: planetary alignment
related: planetary microlensing
related: planetary ring
related: planetesimal
related: polar cap
related: polar region
related: protoplanet
related: resonance gap
related: rill
related: ring division
related: satellite
related: semimajor axis
related: solar nebula
related: solar-planetary relation
related: space exploration
related: structure
related: surface of celestial body
related: synodic period
related: syzygy
related: topography
related: two-body problem
related: volatile
related: volcano
related: water ice

planet satellite
type: Concept
broader: satellite
definition: planet satellite

plasma cloud
type: Concept
broader: cloud
definition: plasma cloud
related: ion
related: plasma
related: plasma jet

plasma jet
type: Concept
broader: jet
definition: plasma jet
related: ion
related: plasma
related: plasma cloud
related: plasma loop

plasma loop
type: Concept
definition: plasma loop
related: plasma
related: plasma jet

plasmapause
type: Concept
definition: plasmapause
related: plasma

plasma physics
type: Concept
definition: plasma physics
related: magnetohydrodynamics
related: plasma

plasma
type: Concept
alternative label: cosmic plasma
broader: particle
definition: plasma
narrower: collisional plasma
narrower: low-temperature plasma
narrower: relativistic plasma
narrower: solar wind
narrower: stellar wind
related: H II region
related: Holtsmark approximation
related: elementary particle
related: energetic particle
related: ion
related: ionized gas
related: plasma cloud
related: plasma jet
related: plasma loop
related: plasma physics
related: plasma wave
related: plasmapause
related: radiation belt
related: radiative recombination
related: thermodynamics
related: viscosity

plasma wave
type: Concept
definition: plasma wave
related: ion plasma wave
related: magnetohydrodynamics
related: plasma

platinum
type: Concept
alternative label: Pt
broader: fundamental chemical element
definition: platinum (atomic number 78)
history note: FVH: new (2007-OCT-25)

Pluto
type: Concept
broader: dwarf planet
definition: Pluto
history note: FVH: new (2007-OCT-2)
related: Solar System

plutonium
type: Concept
alternative label: Pu
broader: fundamental chemical element
definition: plutonium (atomic number 94)
history note: FVH: new (2007-OCT-25)

P magnitude
type: Concept
broader: apparent magnitude
definition: P magnitude
related: far infrared radiation
related: infrared photometry

Pogson scale
type: Concept
definition: Pogson scale
related: magnitude

Poincare theorem
type: Concept
definition: Poincare theorem
related: star cluster
related: stellar dynamics

pointing accuracy
type: Concept
definition: pointing accuracy
related: control system
related: pointing error
related: telescope
related: tracking

pointing error
type: Concept
definition: pointing error
related: control system
related: pointing accuracy
related: telescope
related: tracking

point spread function
type: Concept
alternative label: PSF
broader: transfer function
definition: point spread function
related: atmospheric refraction
related: seeing
related: turbulence Earth atmosphere

polar axis
type: Concept
definition: polar axis
related: celestial pole
related: telescope mounting

polar cap
type: Concept
definition: polar cap
related: Earth
related: planet

polar diagram
type: Concept
definition: polar diagram
related: antenna design
related: beamwidth
related: radio antenna
related: sensitivity
related: sidelobe

polarimeter
type: Concept
broader: optical instrument
broader: telescope instrument
definition: polarimeter
related: photometer
related: polarimetry

polarimetry
type: Concept
broader: astronomical technique
broader: observing technique
definition: polarimetry
related: light polarization
related: photometry
related: polarimeter

polarization charge separation
type: Concept
broader: magneto-optical effect
definition: polarization [charge separation]
related: anisotropy
related: ion

polarized light
type: Concept
alternative label: polarised light UK
broader: electromagnetic radiation
broader: visible radiation
definition: polarized light
related: light polarization

polarized radiation
type: Concept
broader: electromagnetic radiation
broader: radiation
definition: polarized radiation
related: Faraday effect
related: X-ray polarization
related: light polarization
related: stokes parameter

polar motion
type: Concept
broader: motion
definition: polar motion
related: Chandler wobble
related: Earth rotation
related: latitude variation
related: nutation
related: precession

polar orbit
type: Concept
broader: orbit
definition: polar orbit
related: artificial satellite

polar region
type: Concept
definition: polar region
related: planet

polar tide
type: Concept
broader: tide
definition: polar tide

pole
type: Concept
definition: pole
narrower: Galactic pole
narrower: celestial pole
narrower: ecliptic pole
narrower: nadir
narrower: zenith

polishing
type: Concept
definition: polishing
narrower: figuring
related: lens
related: mirror
related: optical surface

pollution
type: Concept
definition: pollution
narrower: air pollution
narrower: light pollution
narrower: space pollution
related: greenhouse effect
related: site testing

polonium
type: Concept
alternative label: Po
broader: fundamental chemical element
definition: polonium (atomic number 84)
history note: FVH: new (2007-OCT-25)

polycyclic hydrocarbon
type: Concept
broader: hydrocarbon
definition: polycyclic hydrocarbon

polytrope
type: Concept
definition: polytrope
related: model
related: stellar structure

population II Cepheid
type: Concept
broader: population II star
definition: Population II Cepheid
narrower: RR Lyrae star
narrower: W Virginis star

population III star
type: Concept
alternative label: PopIII
broader: metal-poor star
broader: old star
broader: star
definition: Population III star
history note: FVH: new (2007-SEP-21)
narrower: halo star
related: Galactic halo
related: globular star cluster
related: stellar population

population II star
type: Concept
alternative label: Pop II star
alternative label: PopII
broader: metal-poor star
broader: old star
broader: star
definition: Population II star
narrower: SX Phoenicis star
narrower: disk population
narrower: disk star
narrower: halo star
narrower: horizontal branch star
narrower: population II Cepheid
related: Galactic halo
related: galactic nucleus
related: globular star cluster
related: intermediate population star
related: stellar population
related: subluminous star

population inversion
type: Concept
definition: population inversion
related: atomic process
related: laser
related: maser
related: stimulated emission

population I star
type: Concept
alternative label: PopI
broader: star
definition: Population I star
narrower: extreme population I star
narrower: young star
related: open star cluster
related: spiral arm
related: stellar population
related: young star cluster

position angle
type: Concept
broader: orbital element
definition: position angle
related: binary star
related: orbit
related: orientation

position
type: Concept
definition: position
narrower: apparent position
narrower: true position
related: coordinate system
related: fundamental system
related: reference system
related: spherical coordinate
related: standard star
scope note: combine with other terms

position sensitive proportional counter
type: Concept
alternative label: PSPC
broader: proportional counter
definition: position-sensitive proportional counter
history note: FVH: new (2007-SEP-21)

positron
type: Concept
broader: antiparticle
broader: lepton
broader: nuclear radiation
broader: particle
definition: positron
related: electron
related: pair annihilation
related: pair production
related: radioactivity

post-asymptotic giant branch
type: Concept
alternative label: post-AGB
definition: post-asymptotic giant branch
history note: APM: new (2007-OCT-4)
narrower: UU Herculis star
related: Hertzsprung-Russell diagram
related: asymptotic giant branch
related: late-type giant

post-main sequence star
type: Concept
alternative label: post main sequence star
broader: evolved star
broader: non-main sequence star
definition: post-main sequence star
narrower: giant
narrower: subgiant
narrower: supergiant
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list; excluding advanced evolution

potassium
type: Concept
alternative label: K
broader: fundamental chemical element
definition: potassium (atomic number 19)
history note: FVH: new (2007-OCT-25)

potential energy
type: Concept
broader: energy
definition: potential energy
related: kinetic energy

potential theory
type: Concept
definition: potential theory
scope note: in mathematics

power
type: Concept
definition: power
scope note: combine with other terms

Poynting-Robertson effect
type: Concept
alternative label: Poynting Robertson effect
definition: Poynting-Robertson effect
related: radiation pressure
related: solar wind
related: stellar wind

p process
type: Concept
definition: p-process
related: nucleosynthesis
related: r-process
related: s-process
related: supernova

praseodymium
type: Concept
alternative label: Pr
broader: fundamental chemical element
broader: rare earth
definition: praseodymium (atomic number 59)
history note: FVH: new (2007-OCT-25)

preamplifier
type: Concept
broader: amplifier
definition: preamplifier

precession
type: Concept
definition: precession
related: Earth rotation
related: astrometry
related: celestial mechanics
related: equation of the equinox
related: nutation
related: obliquity of ecliptic
related: polar motion
related: superhump

precision
type: Concept
definition: precision
related: limiting magnitude
related: sensitivity
scope note: combine with other terms

precursor pulse
type: Concept
definition: precursor pulse
related: pulsar

prediction
type: Concept
definition: prediction
related: forecasts
scope note: combine with other terms

pre-Galactic star
type: Concept
alternative label: pregalactic star
broader: old star
definition: pre-Galactic star

pre-main sequence star
type: Concept
alternative label: early stage star
alternative label: premainsequence star
broader: non-main sequence star
broader: young star
definition: pre-main sequence star
narrower: Herbig-Haro object
narrower: RW Aurigae star
narrower: T Tauri star
narrower: flash star
narrower: protostar
related: T association
related: orion population star
related: star formation

pre-nova
type: Concept
alternative label: prenova
broader: progenitor
definition: pre-nova
related: nova

pre-solar nebula
type: Concept
alternative label: presolar nebula
definition: pre-solar nebula
related: Solar System

pressure broadening
type: Concept
broader: line broadening
definition: pressure broadening
related: Doppler broadening
related: Zeeman splitting
related: line spectrum
related: natural line width
related: spectroscopy

pressure
type: Concept
definition: pressure
related: Rankine-Hugoniot relation
related: barometer
related: radiation pressure
related: vacuum
scope note: combine with other terms

pre-supernova
type: Concept
alternative label: presupernova
broader: progenitor
definition: pre-supernova
related: supernova

primary lens
type: Concept
broader: lens
broader: objective
definition: primary lens
related: refracting telescope

primary mirror
type: Concept
broader: mirror
broader: objective
broader: telescope mirror
definition: primary mirror
related: reflecting telescope
related: secondary mirror
related: tertiary mirror

primary star
type: Concept
broader: companion star
definition: primary star
history note: ES: new (2007-OCT-8)
related: secondary star
related: tertiary star

prime focus
type: Concept
broader: focus
definition: prime focus
related: Cassegrain focus
related: Coude focus
related: Nasmyth focus

primordial fireball
type: Concept
broader: cosmology
definition: primordial fireball
related: Big Bang theory

primordial galaxy
type: Concept
broader: galaxy
definition: primordial galaxy

prism
type: Concept
definition: prism
narrower: objective prism
related: grism
related: optical instrument
related: prism spectrograph
related: spectrograph
related: spectrum

prism spectrograph
type: Concept
broader: spectrograph
definition: prism spectrograph
related: grating spectrograph
related: prism

profile
type: Concept
definition: profile
narrower: line profile

progenitor
type: Concept
alternative label: precursors
definition: progenitor
narrower: pre-nova
narrower: pre-supernova
related: nova
related: supernova

promethium
type: Concept
alternative label: Pm
broader: fundamental chemical element
definition: promethium (atomic number 61)
history note: FVH: new (2007-OCT-25)

prominence
type: Concept
alternative label: chromospheric eruption
definition: prominence
narrower: active prominence
narrower: quiescent prominence
related: Hanle effect
related: Sun
related: chromosphere
related: flare
related: optical flare
related: solar activity
related: solar filament
related: sunspot

propagation
type: Concept
definition: propagation
scope note: combine with other terms

proper motion
type: Concept
broader: motion
broader: space motion
definition: proper motion
related: Galactic rotation
related: Local Standard of Rest
related: kinematics
related: moving cluster parallax
related: peculiar motion
related: photographic astrometry
related: radial velocity
related: radiant moving cluster
related: secular parallax
related: stellar dynamics
related: stellar motion
related: transverse velocity

property
type: Concept
definition: property
narrower: magnetic property
narrower: mechanical property
narrower: optical property
narrower: surface property
narrower: thermal property
scope note: combine with other terms

proportional counter
type: Concept
broader: measuring instrument
change note: FVH: added NT POSITION_SENSITIVE_PROPORTIONAL_COUNTERS (2007-SEP-21)
definition: proportional counter
narrower: position sensitive proportional counter
related: X-ray detector

protactinium
type: Concept
alternative label: Pa
broader: fundamental chemical element
definition: protactinium (atomic number 91)
history note: FVH: new (2007-OCT-25)

protocluster
type: Concept
broader: cluster
definition: protocluster
related: collapsing cloud
related: cosmogony
related: cosmology
related: galaxy cluster
related: star cluster

protogalaxy
type: Concept
broader: galaxy
broader: gaseous sphere
definition: protogalaxy
related: collapsing cloud
related: cosmogony
related: cosmology

proton
type: Concept
broader: elementary particle
broader: fundamental particle
broader: particle
definition: proton
related: alpha particle
related: antiproton
related: nucleus atom

proton-proton reaction
type: Concept
alternative label: proton proton cycle
alternative label: proton proton reaction
alternative label: proton-proton cycle
broader: hydrogen burning
definition: proton-proton reaction
related: carbon nitrogen cycle
related: nuclear fusion
related: stellar interior

protoplanetary nebula
type: Concept
alternative label: proplyds
broader: collapsing cloud
change note: FVH: added ALT proplyd (2007-SEP-21)
definition: protoplanetary nebula
related: cosmogony
related: protoplanet
related: solar nebula

protoplanet
type: Concept
definition: protoplanet
related: Solar System
related: planet
related: planetesimal
related: protoplanetary nebula
related: satellite
related: solar nebula

protostar
type: Concept
broader: gaseous sphere
broader: pre-main sequence star
definition: protostar
related: Bok globule
related: Herbig-Haro object
related: T Tauri star
related: birth rate
related: collapsing cloud
related: cometary globule
related: star formation
related: stellar evolution

pulsar
type: Concept
broader: collapsed star
broader: degenerate star
broader: evolved star
broader: radio source
broader: relativistic star
definition: pulsar
narrower: X-ray pulsar
narrower: binary pulsar
narrower: optical pulsar
narrower: radio pulsar
related: frequency shift
related: glitch
related: neutron star
related: precursor pulse
related: pulse duration
related: pulse energy
related: pulse intensity
related: pulse profile
related: pulse structure
related: pulse width
related: pulse window
related: rapid oscillation
related: supernova
related: supernova remnant

pulsating variable star
type: Concept
broader: intrinsic variable star
broader: variable star
definition: pulsating variable star
narrower: 53 Persei star
narrower: BL Herculis star
narrower: Cepheid
narrower: Mira variable star
narrower: RR Lyrae star
narrower: RV Tauri star
narrower: S Vulpeculae star
narrower: SX Phoenicis star
narrower: W Virginis star
narrower: ZZ Ceti star
narrower: beta Cephei star
narrower: delta delphini star
narrower: delta Scuti star
narrower: double-mode Cepheid
narrower: double-mode variable star
narrower: dwarf Cepheid
narrower: irregular variable star
narrower: lambda eridani star
narrower: long period variable star
narrower: multi-periodic variable star
narrower: periodic variable star
narrower: semi-regular variable star
related: He II ionization zone
related: asteroseismology
related: double-mode pulsation
related: kappa mechanism
related: multi-periodic pulsation
related: non-radial pulsation
related: overtone mode
related: period
related: period change
related: period-color relation
related: period-density relation
related: period-luminosity-color relation
related: period-luminosity relation
related: period-mass relation
related: period-radius relation
related: period-spectrum relation
related: pulsation mode
related: pulsation theory

pulsation mode
type: Concept
definition: pulsation mode
narrower: fundamental mode
narrower: overtone mode
related: multi-periodic pulsation
related: multi-periodic variable star
related: non-radial pulsation
related: period
related: pulsating variable star
related: pulsation
related: pulsation theory

pulsation
type: Concept
definition: pulsation
related: amplitude
related: asteroseismology
related: pulsation mode
scope note: combine with other terms

pulsation theory
type: Concept
definition: pulsation theory
related: He II ionization zone
related: pulsating variable star
related: pulsation mode

pulse counter
type: Concept
definition: pulse counter
related: amplifier
related: pulse

pulse counting
type: Concept
definition: pulse counting
related: amplifier
related: pulse

pulse duration
type: Concept
definition: pulse duration
related: pulsar
related: pulse

pulse energy
type: Concept
definition: pulse energy
related: pulsar
related: pulse

pulse intensity
type: Concept
definition: pulse intensity
related: pulsar
related: pulse

pulse profile
type: Concept
definition: pulse profile
related: pulsar
related: pulse

pulse
type: Concept
definition: pulse
related: pulse counter
related: pulse counting
related: pulse duration
related: pulse energy
related: pulse intensity
related: pulse profile
related: pulse structure
related: pulse width
related: pulse window
scope note: combine with other terms

pulse structure
type: Concept
definition: pulse structure
related: pulsar
related: pulse

pulse width
type: Concept
definition: pulse width
related: pulsar
related: pulse

pulse window
type: Concept
definition: pulse window
related: pulsar
related: pulse

Purkinje effect
type: Concept
definition: Purkinje effect
related: photometry
related: variable star
related: visual magnitude
related: visual observation

q branch
type: Concept
definition: q-branch
related: molecular spectrum
related: vibrational spectrum

Q magnitude
type: Concept
broader: apparent magnitude
definition: Q magnitude
related: far infrared radiation
related: infrared photometry

quadrant detector
type: Concept
definition: quadrant detector
related: autoguider
related: control system
related: guide system
related: photomultiplier tube

quadrant
type: Concept
broader: astrometric instrument
broader: instrument
definition: quadrant
related: meridian circle

quadrature
type: Concept
definition: quadrature
related: conjunction
related: opposition

quanta
type: Concept
alternative label: quantum
definition: quanta
related: photon
related: quantum theory

quantization
type: Concept
alternative label: quantisation UK
definition: quantization
related: analysis
related: determination
related: measurement

quantum cosmology
type: Concept
broader: cosmology
definition: quantum cosmology
related: naked singularity
related: space-time singularity

quantum efficiency
type: Concept
alternative label: Q.E.
alternative label: QE
definition: quantum efficiency
related: cathode
related: charge-coupled device
related: detector
related: image tube
related: photographic emulsion
related: photomultiplier tube

quantum field theory
type: Concept
definition: quantum field theory
related: electromagnetic field
related: gravitational field
related: quantum theory

quantum mechanics
type: Concept
definition: quantum mechanics
related: Fermi-Dirac statistics
related: quantum theory
related: relativistic velocity
related: superconducting tunnel junction

quantum theory
type: Concept
definition: quantum theory
related: quanta
related: quantum field theory
related: quantum mechanics

quark
type: Concept
broader: elementary particle
definition: quark
related: baryon
related: lepton
related: meson
related: neutron star

quarter wave plate
type: Concept
definition: quarter-wave plate
history note: FVH: new (2007-SEP-21)
related: circular polarization
related: half-wave plate

quasar galaxy pair
type: Concept
definition: quasar-galaxy pair
related: galaxy
related: quasar

quasar microlensing
type: Concept
broader: gravitational microlensing
definition: microlensing of AGN nucleus
history note: FVH: new (2007-OCT-8)
related: quasar

quasar
type: Concept
alternative label: QSO
alternative label: quasi-stellar galaxy
alternative label: quasi-stellar object
alternative label: quasi-stellar radio_source
broader: extragalactic object
broader: extragalactic radio source
definition: quasar
narrower: X-ray quasar
narrower: radio quiet quasar
related: BL Lacertae object
related: Lyman alpha forest
related: X-ray source
related: absorption line system
related: active galactic nucleus
related: blazar
related: compact galaxy
related: double quasar
related: liner galaxy
related: luminous arc
related: quasar galaxy pair
related: quasar microlensing
related: variable source

quiescent prominence
type: Concept
broader: prominence
definition: quiescent prominence
related: Sun
related: chromosphere

quiet Sun
type: Concept
definition: quiet Sun
related: active Sun
related: solar cycle

radar astronomy
type: Concept
broader: radio astronomy
definition: radar astronomy
related: radar
related: radar equipment
related: radar telescope
related: radio observatory

radar equipment
type: Concept
definition: radar equipment
narrower: antenna
related: radar astronomy
related: radio telescope

radar mapping
type: Concept
definition: radar mapping
related: map

radar
type: Concept
definition: radar
narrower: optical radar
related: Doppler effect
related: antenna
related: radar astronomy

radar telescope
type: Concept
broader: radio telescope
definition: radar telescope
related: dish antenna
related: parabolic reflector
related: radar astronomy

radial pulsation
type: Concept
definition: radial pulsation
related: BL Herculis star
related: Cepheid
related: He II ionization zone
related: Mira variable star
related: RV Tauri star
related: beta Cephei star
related: delta Scuti star

radial velocity
type: Concept
broader: space motion
broader: velocity
definition: radial velocity
narrower: iodine cell
related: Doppler effect
related: kinematics
related: line shift
related: peculiar motion
related: peculiar velocity
related: proper motion
related: redshift
related: spectroscopy
related: stellar dynamics
related: stellar motion
related: tangential velocity
related: transverse velocity
related: virial theorem

radiant meteor
type: Concept
definition: radiant [meteor]
related: meteor
related: meteor shower
related: meteor stream
related: meteor trail

radiant moving cluster
type: Concept
definition: radiant [moving cluster]
related: moving cluster parallax
related: open star cluster
related: proper motion

radiation belt
type: Concept
definition: radiation belt
narrower: van Allen radiation belt
related: Earth
related: atmosphere
related: plasma

radiation damping
type: Concept
definition: radiation damping
related: damping constant
related: decay oscillation
related: radiative braking

radiation field
type: Concept
definition: radiation field
related: electromagnetic field

radiation mechanism
type: Concept
definition: radiation mechanism
narrower: free-bound emission
narrower: free-free emission
related: Cerenkov radiation
related: Rayleigh limit
related: bremsstrahlung
related: cyclotron radiation
related: gravitational radiation
related: non-LTE transfer
related: relativistic particle
related: relativistic plasma
related: synchrotron radiation

radiation pressure
type: Concept
definition: radiation pressure
related: Eddington limit
related: Poynting-Robertson effect
related: photon
related: pressure
related: solar wind
related: stellar wind

radiation
type: Concept
change note: FVH: moved lots of NT's to electromagnetic_radiation (2007-OCT-8)
definition: radiation
narrower: Cerenkov radiation
narrower: X-ray radiation
narrower: background radiation
narrower: continuum radiation
narrower: cosmic ray
narrower: cyclotron radiation
narrower: electromagnetic radiation
narrower: gamma-ray radiation
narrower: gravitational radiation
narrower: high-energy radiation
narrower: infrared radiation
narrower: polarized radiation
narrower: synchrotron radiation
narrower: thermal radiation
narrower: ultraviolet radiation
related: Planck black body formula
related: absorption
related: albedo
related: bolometer
related: effective temperature
related: emissivity
related: energy-transfer
related: flux density
related: illumination
related: irradiance
related: opacity
related: photon
related: radiative equilibrium
related: recombination line
related: solar constant
scope note: combine with other terms

radiation scattering
type: Concept
alternative label: electromagnetic wave scattering
definition: radiation scattering
narrower: Compton scattering
narrower: Rayleigh scattering
narrower: Thomson scattering
narrower: X-ray scattering
narrower: light scattering
related: Compton effect
related: Raman effect
related: electrostatic wave
related: elementary particle scattering
related: light polarization
related: phase function
related: photon
related: scattering
related: zodiacal light

radiative braking
type: Concept
definition: radiative braking
related: damping constant
related: dynamical friction
related: radiation damping
related: rotating star

radiative equilibrium
type: Concept
definition: radiative equilibrium
related: absorption
related: electromagnetic radiation
related: radiation
related: temperature

radiative recombination
type: Concept
alternative label: radiative capture
definition: radiative recombination
related: airglow
related: electron
related: photon
related: plasma

radiative transfer
type: Concept
broader: energy-transfer
definition: radiative transfer
related: Rayleigh limit
related: opacity
related: transport process

radical
type: Concept
broader: composite particle
definition: radical
narrower: hydroxyl radical
related: ion

radio absorption
type: Concept
definition: radio absorption
related: H I region
related: interstellar matter
related: ionosphere

radioactive decay
type: Concept
definition: radioactive decay
related: radioactivity

radioactivity
type: Concept
definition: radioactivity
related: alpha particle
related: electron
related: gamma-ray radiation
related: nuclear fission
related: positron
related: radioactive decay

radio antenna
type: Concept
alternative label: radio antennas
broader: antenna
definition: radio antennas
related: polar diagram
related: radio telescope
related: sidelobe

radio astrometry
type: Concept
broader: astrometry
broader: observing technique
broader: radio astronomy
definition: radio astrometry
related: interferometry
related: long baseline interferometry
related: very long baseline interferometry

radio astronomy
type: Concept
definition: radio astronomy
narrower: millimeter astronomy
narrower: radar astronomy
narrower: radio astrometry
narrower: submillimeter astronomy
related: clean method
scope note: use as nts all terms associated with radio astronomy

radio background
type: Concept
alternative label: radio frequency interference
alternative label: radio noise
broader: background radiation
definition: radio background
related: X-ray background
related: cosmic noise
related: gamma-ray background
related: microwave background
related: radio interference
related: radio radiation
related: ultraviolet background

radio burst
type: Concept
broader: burst
definition: radio burst
related: X-ray burst
related: burster
related: gamma-ray burst
related: optical burst

radio core
type: Concept
definition: radio core
related: radio source

radio emission
type: Concept
broader: emission spectrum
definition: radio emission
scope note: see radio radiation

radio flare
type: Concept
broader: flare
definition: radio flare
related: flare star

radio frequency
type: Concept
definition: radio frequency
related: 21-cm line
related: Paul trap
related: radio radiation
related: radio spectrum
related: spectral index

radio galaxy
type: Concept
broader: extragalactic radio source
broader: galaxy
definition: radio galaxy
narrower: Ep galaxy
narrower: giant radio galaxy
narrower: head tail galaxy
related: Fanaroff-Riley class
related: X-ray source
related: active galactic nucleus

radioheliograph
type: Concept
broader: radio telescope
broader: solar telescope
definition: radioheliograph

radio interference
type: Concept
alternative label: radio frequency interference
alternative label: radio noise
definition: radio interference
narrower: cosmic noise
related: radio background

radio interferometer
type: Concept
broader: interferometer
broader: radio telescope
definition: radio interferometer
narrower: long baseline interferometer
narrower: t array
narrower: very long baseline interferometer
narrower: y array
related: array
related: pencil beam
related: phased array
related: radio interferometry
related: radio observatory

radio interferometry
type: Concept
broader: interferometry
broader: observing technique
definition: radio interferometry
narrower: long baseline interferometry
narrower: very long baseline interferometry
related: interference wave
related: radio interferometer
related: time synchronization
scope note: see radio interferometer

radio jet
type: Concept
broader: jet
definition: radio jet
related: radio source

radiometer
type: Concept
broader: detector
broader: measuring instrument
definition: radiometer
narrower: Dicke radiometer
related: bolometer
related: photometer
related: radiometry

radiometry
type: Concept
definition: radiometry
related: radiometer

radio observatory
type: Concept
broader: observatory
definition: radio observatory
related: millimeter astronomy
related: radar astronomy
related: radio interferometer
related: radio telescope
related: submillimeter astronomy

radio occultation
type: Concept
broader: occultation
definition: radio occultation

radio pulsar
type: Concept
broader: pulsar
definition: radio pulsar
related: optical pulsar

radio quiet quasar
type: Concept
broader: quasar
definition: radio quiet quasar

radio radiation
type: Concept
alternative label: radio wave
broader: electromagnetic radiation
change note: FVH: moved BT radiation to BT electromagnetic_radiation and radio_wave to ALT (2007-OCT-8)
definition: radio radiation
related: Jansky
related: radio background
related: radio frequency
related: radio source
scope note: synonym: radio emission

radio recombination line
type: Concept
broader: recombination line
definition: radio recombination line
narrower: 21-cm line
related: H I region
related: H II region
related: maser

radio source catalog
type: Concept
broader: catalog
definition: radio source catalog
related: radio source count
scope note: combine with other terms

radio source count
type: Concept
definition: radio source count
related: observational cosmology
related: radio source
related: radio source catalog
related: statistics
related: survey

radio source
type: Concept
broader: source
definition: radio source
narrower: OH source
narrower: compact source
narrower: discrete radio source
narrower: extended source
narrower: extragalactic radio source
narrower: head tail galaxy
narrower: pulsar
narrower: radio star
narrower: variable source
related: SiO maser
related: bipolar outflow
related: galaxy encounter
related: interplanetary scintillation
related: interstellar scintillation
related: ionospheric scintillation
related: jet
related: lobe
related: maser
related: optical identification
related: radio core
related: radio jet
related: radio radiation
related: radio source count
related: supernova remnant
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

radio spectrograph
type: Concept
alternative label: radio spectrometer
broader: spectrograph
definition: radio spectrograph
related: radio spectroscopy
related: radio spectrum

radio spectroscopy
type: Concept
definition: radio spectroscopy
related: radio spectrograph
related: radio spectrum

radio spectrum
type: Concept
broader: spectrum
definition: radio spectrum
related: microwave spectrum
related: radio frequency
related: radio spectrograph
related: radio spectroscopy
related: spectral index

radio star
type: Concept
broader: radio source
definition: radio star
narrower: flare star
related: X-ray star

radio structure
type: Concept
definition: radio structure
narrower: lobe
related: bipolar outflow
related: compact source
related: contour map
related: drift scan
related: extended source
related: head tail galaxy

radio telescope
type: Concept
broader: telescope
definition: radio telescope
narrower: Cassegrain antenna
narrower: Mills cross antenna
narrower: Yagi antenna
narrower: dish antenna
narrower: radar telescope
narrower: radio interferometer
narrower: radioheliograph
narrower: very long baseline interferometer
related: antenna
related: antenna design
related: apodization
related: array
related: beam switching
related: beamwidth
related: feed horn
related: half-wave dipole
related: interferometer
related: parabolic reflector
related: phase rotator
related: phase switching
related: radar equipment
related: radio antenna
related: radio observatory
related: receiver
related: shaped reflector
related: subreflector
scope note: not a complete list of terms

radio transmission window
type: Concept
broader: atmospheric window
change note: FVH: renamed to avoid confusion with optics (2007-NOV-2)
definition: radio transmission window through the atmosphere
related: infrared transmission window
related: interstellar matter
related: optical transmission window
scope note: low absorption in atmosphere

radio waveguide
type: Concept
broader: waveguide
definition: radio waveguide
narrower: horn antenna

radium
type: Concept
alternative label: Ra
broader: fundamental chemical element
definition: radium (atomic number 88)
history note: FVH: new (2007-OCT-25)

radius-luminosity relation
type: Concept
alternative label: radius luminosity relation
broader: statistical relation
definition: radius-luminosity relation
narrower: fundamental plane
related: Cepheid
related: period-color relation
related: period-density relation
related: period-luminosity-color relation
related: period-luminosity relation
related: period-mass relation
related: period-radius relation
related: period-spectrum relation

radon
type: Concept
alternative label: Rn
broader: fundamental chemical element
definition: radon (atomic number 86)
history note: FVH: new (2007-OCT-25)

RAID array
type: Concept
broader: data storage
definition: RAID array of hard disk
history note: FVH: new (2007-NOV-2)

Raman effect
type: Concept
definition: Raman effect
related: Raman scattering
related: Raman spectroscopy
related: Raman spectrum
related: absorption spectrum
related: emission spectrum
related: radiation scattering

Raman scattering
type: Concept
definition: Raman scattering
related: Raman effect
scope note: see Raman effect

Raman spectroscopy
type: Concept
broader: spectroscopy
definition: Raman spectroscopy
related: Raman effect
related: molecular spectrum
scope note: see Raman effect

Raman spectrum
type: Concept
definition: Raman spectrum
related: Raman effect
related: light scattering
scope note: see Raman effect

Ramsden eyepiece
type: Concept
broader: eyepiece
definition: Ramsden eyepiece

range finder
type: Concept
broader: measuring instrument
definition: range finder
related: distance

Rankine-Hugoniot relation
type: Concept
definition: Rankine-Hugoniot relation
related: density
related: pressure
related: shock wave

rapid burst
type: Concept
broader: burst
definition: rapid burst
related: X-ray burst
related: gamma-ray burst

rapid oscillation
type: Concept
definition: rapid oscillation
related: Ap star
related: asteroseismology
related: pulsar

rare earth
type: Concept
broader: fundamental chemical element
definition: rare earth
narrower: cerium
narrower: dysprosium
narrower: erbium
narrower: europium
narrower: gadolinium
narrower: holmium
narrower: lanthanum
narrower: lutetium
narrower: neodymium
narrower: praseodymium
narrower: samarium
narrower: scandium
narrower: terbium
narrower: thulium
narrower: ytterbium
narrower: yttrium
related: abundance
related: metal abundance
related: metal line

R association
type: Concept
alternative label: R-association
broader: star association
definition: R association
related: reflection nebula
related: young star

ratio
type: Concept
definition: ratio
history note: ES: new (2007-OCT-11)
narrower: axial ratio

Rayleigh
type: Concept
definition: Rayleigh
related: aurora
related: night sky brightness
scope note: solar aurora flux unit

Rayleigh criterion
type: Concept
alternative label: Rayleigh limit
definition: Rayleigh criterion
related: diffraction
related: resolution

Rayleigh limit
type: Concept
definition: Rayleigh limit
related: radiation mechanism
related: radiative transfer
scope note: refers to radiation mechanism

Rayleigh number
type: Concept
definition: Rayleigh number
related: convection
related: thermal stability

Rayleigh scattering
type: Concept
broader: light scattering
broader: radiation scattering
definition: Rayleigh scattering
related: Compton scattering
related: Mie scattering
related: Thomson scattering
related: airglow
related: interstellar absorption
related: night sky brightness

Rayleigh-Taylor instability
type: Concept
broader: instability
definition: Rayleigh-Taylor instability
related: fluid mechanics

ray
type: Concept
definition: lunar ray
related: Moon
scope note: refers to lunar feature

Razin effect
type: Concept
definition: Razin effect
related: synchrotron radiation
scope note: also Razin-Tsytovich effect

R Canis Majoris star
type: Concept
alternative label: R CMa star
broader: eclipsing binary star
definition: R Canis Majoris star

R Coronae Borealis star
type: Concept
alternative label: R Cor Bor star
alternative label: RCB star
broader: irregular variable star
definition: R Coronae Borealis star
related: circumstellar dust
related: circumstellar grain
related: supergiant

read out noise
type: Concept
alternative label: RON
broader: noise
definition: read-out noise
history note: FVH: new (2007-SEP-21)
related: charge-coupled device

real anomaly
type: Concept
broader: orbital anomaly
definition: real anomaly

receiver
type: Concept
definition: receiver
related: correlation
related: detector
related: interferometric correlation
related: phase sensitive detector
related: phase switching
related: radio telescope

recombination line
type: Concept
broader: emission line
definition: recombination line
narrower: radio recombination line
related: electromagnetic radiation
related: radiation
related: recombination
related: spectrum

recombination
type: Concept
definition: recombination
related: electron
related: photoionization
related: recombination line

recurrent nova
type: Concept
broader: nova
definition: recurrent nova
related: fast nova
related: slow nova

reddened star
type: Concept
definition: reddened star
related: absorption
related: interstellar absorption
related: interstellar reddening
related: reddening
related: reddening law

reddening law
type: Concept
definition: reddening law
related: gas to dust ratio
related: interstellar reddening
related: reddened star
related: selective absorption

reddening
type: Concept
definition: reddening
narrower: interstellar reddening
related: absorption
related: intergalactic absorption
related: interstellar absorption
related: interstellar dust
related: interstellar gas
related: intrinsic color
related: reddened star
related: selective absorption

red dwarf flare star
type: Concept
broader: flare star
broader: late-type dwarf
definition: red dwarf flare star

red dwarf
type: Concept
definition: red dwarf star
scope note: see late-type dwarf star

red giant bump
type: Concept
alternative label: red bump
broader: giant branch
definition: red giant bump
history note: ES: new (2007-OCT-8)
related: metal-rich star

red giant clump
type: Concept
alternative label: red clump
broader: giant branch
definition: red giant clump
history note: ES: new (2007-OCT-8)

red giant
type: Concept
definition: red giant star
scope note: see late-type giant star

red giant tip
type: Concept
broader: giant branch
definition: red giant tip
related: Hertzsprung-Russell diagram
related: RGB tip distance
related: carbon flash
related: evolved star
related: helium flash
related: late-type giant

redshift distance relation
type: Concept
definition: redshift-distance relation
related: Dark Energy
related: cosmological distance scale
related: cosmology
related: observational cosmology

redshift magnitude relation
type: Concept
definition: redshift-magnitude relation
related: Dark Energy
related: Hubble constant
related: Hubble diagram
related: Hubble law
related: cosmological distance scale
related: cosmology

redshift
type: Concept
alternative label: red shift
broader: Doppler effect
broader: line shift
definition: redshift
narrower: gravitational redshift
related: Hubble diagram
related: Hubble law
related: Lyman alpha forest
related: Tully-Fisher relation
related: cosmological distance scale
related: cosmology
related: frequency shift
related: k correction
related: observational cosmology
related: radial velocity

red star
type: Concept
definition: red star
scope note: see either late-type star or reddened star

red supergiant
type: Concept
definition: red supergiant star
scope note: see late-type supergiant star

reduction method
type: Concept
definition: reduction method
related: analysis
related: astronomical technique
related: data processing
related: data reduction

reference frame
type: Concept
definition: reference frame
related: coordinate system

reference system
type: Concept
definition: reference system
related: astrometry
related: coordinate system
related: position
related: spherical coordinate

reflecting telescope
type: Concept
alternative label: reflector
broader: optical telescope
definition: reflecting telescope
narrower: Baker-Nunn camera
narrower: Bouwers telescope
narrower: Maksutov telescope
narrower: Ritchey-Chretien telescope
narrower: Schmidt telescope
narrower: coelostat
narrower: multiple mirror telescope
narrower: wide-field telescope
related: parabolic reflector
related: primary mirror
related: secondary mirror
related: tertiary mirror
scope note: refers to optical telescope

reflection grating
type: Concept
broader: diffraction grating
definition: reflection grating
related: echelle grating
related: objective grating
related: transmission grating

reflection nebula
type: Concept
broader: interstellar matter
broader: nebula
definition: reflection nebula
related: R association

reflection
type: Concept
definition: reflection
related: albedo
related: mirror
related: refraction
related: scattering
related: thin film
related: transmission

reflector antenna
type: Concept
alternative label: reflector antennas
broader: antenna
definition: reflector antenna

refracting telescope
type: Concept
broader: optical telescope
definition: refracting telescope
narrower: zenith telescope
related: primary lens

refraction angle
type: Concept
alternative label: angle of refraction
definition: angle of refraction
related: atmosphere
related: zenith distance
scope note: in Earth's atmosphere

refraction
type: Concept
definition: refraction
related: electromagnetic radiation
related: lens
related: reflection
related: refractive index
related: scattering
related: transmission
related: visible radiation
related: wave propagation

refractive index
type: Concept
broader: optical property
definition: refractive index
related: atmospheric refraction
related: lens
related: optical pathlength
related: optics
related: refraction

regression of node
type: Concept
definition: regression of node
related: Moon
related: orbital element

relativistic astrophysics
type: Concept
definition: relativistic astrophysics
related: black hole
related: cosmology
related: gravity
related: neutron star
related: relativistic cosmology

relativistic cosmology
type: Concept
broader: cosmology
definition: relativistic cosmology
related: relativistic astrophysics

relativistic disk
type: Concept
definition: relativistic discs UK
definition: relativistic disk
related: relativistic effect
related: relativistic electron
related: relativistic plasma
related: relativity

relativistic effect
type: Concept
definition: relativistic effect
related: relativistic disk
related: relativistic electron
related: relativistic plasma
related: relativity

relativistic electron
type: Concept
broader: electron beam
broader: relativistic particle
definition: relativistic electron
related: relativistic disk
related: relativistic effect
related: synchrotron radiation

relativistic fluid dynamics
type: Concept
broader: fluid dynamics
broader: relativistic mechanics
definition: relativistic fluid dynamics

relativistic mechanics
type: Concept
definition: relativistic mechanics
narrower: relativistic fluid dynamics
related: relativity

relativistic particle
type: Concept
broader: particle
definition: relativistic particle
narrower: relativistic electron
related: radiation mechanism

relativistic plasma
type: Concept
alternative label: relativistic gas
broader: gas
broader: plasma
definition: relativistic plasma
related: radiation mechanism
related: relativistic disk
related: relativistic effect
related: relativity

relativistic star
type: Concept
definition: relativistic star
narrower: black hole
narrower: neutron star
narrower: pulsar
related: X-ray source
related: relativity

relativistic velocity
type: Concept
broader: velocity
definition: relativistic velocity
related: Big Bang theory
related: cosmology
related: quantum mechanics
related: relativity

relativity
type: Concept
broader: cosmogony
definition: relativity
narrower: general theory of relativity
related: field equation
related: gravitation
related: inertial coordinate system
related: inertial reference frame
related: relativistic disk
related: relativistic effect
related: relativistic mechanics
related: relativistic plasma
related: relativistic star
related: relativistic velocity

relaxation time
type: Concept
definition: relaxation time
related: age
related: galaxy cluster
related: star cluster
related: stellar dynamics

remote control system
type: Concept
broader: control system
definition: remote control system
related: automated telescope
related: automatic patrol telescope
related: telescope
related: telescope instrument

remote sensing
type: Concept
definition: remote sensing
related: detector
related: infrared radiation
related: microwave radiation

research
type: Concept
definition: research
related: design
related: discoveries
related: observation
related: theory

reseaux
type: Concept
definition: reseaux
related: calibration
related: grid
related: photographic plate
related: spectroscopy

residual intensity
type: Concept
definition: residual intensity
related: absorption line
related: line profile

resolution
type: Concept
definition: resolution
narrower: angular resolution
narrower: spectral resolution
related: Rayleigh criterion
related: interferometry
related: optics
related: pixel
related: sensitivity
related: sidelobe
related: visual acuity

resonance gap
type: Concept
definition: resonance gap
narrower: Kirkwood gap
related: asteroid
related: planet
related: planetary ring
related: shepherd satellite

resonance line
type: Concept
definition: resonance line
narrower: H alpha
narrower: Lyman alpha
related: spectrum
scope note: not a complete list of terms

retardation
type: Concept
definition: retardation
scope note: combine with other terms

reticle
type: Concept
definition: reticle
related: eyepiece
related: graticule
related: grid

reticon array
type: Concept
broader: multi-channel detector
definition: reticon array
related: diode array

rgb photometry
type: Concept
alternative label: red-green-blue photometry
broader: broad band photometry
broader: photometric system
definition: rgb photometry
history note: FVH: new (2007-SEP-21)

RGB tip distance
type: Concept
broader: distance measurement
definition: distance obtained from the tip of the red giant branch
history note: ES: new (2007-OCT-8)
related: red giant tip

rgu photometry
type: Concept
broader: broad band photometry
definition: rgu photometry

rhenium
type: Concept
alternative label: Re
broader: fundamental chemical element
definition: rhenium (atomic number 75)
history note: FVH: new (2007-OCT-25)

rho Cassiopeiae star
type: Concept
alternative label: rho Cas star
definition: rho Cassiopeiae star

rhodium
type: Concept
alternative label: Rh
broader: fundamental chemical element
definition: rhodium (atomic number 45)
history note: FVH: new (2007-OCT-25)

Right Ascension
type: Concept
alternative label: celestial longitude
broader: equatorial coordinate system
broader: longitude
definition: Right Ascension
related: Declination
related: celestial equator
related: equator
related: hour angle
related: transit time

rigid body rotation
type: Concept
broader: rotation
definition: rigid body rotation
related: rotating body

rill
type: Concept
definition: rill
related: planet
related: satellite

ring division
type: Concept
definition: ring division
related: planet
related: planetary ring

ring galaxy
type: Concept
broader: galaxy
broader: peculiar galaxy
definition: ring galaxy
related: ring

ring nebula
type: Concept
broader: nebula
definition: ring nebula
related: planetary nebula

ring
type: Concept
definition: ring
narrower: planetary ring
narrower: stellar ring
related: ansa
related: ring galaxy

Ritchey-Chretien telescope
type: Concept
alternative label: RC
broader: reflecting telescope
definition: Ritchey-Chretien telescope

R magnitude
type: Concept
broader: apparent magnitude
definition: R magnitude
related: Bessel photometry
related: Johnson photometry
related: Kron-Cousins photometry

Roche limit
type: Concept
definition: Roche limit
related: close binary star
related: gravitation
related: orbit
related: planet
related: planetary ring
related: tidal disruption

Roche lobe
type: Concept
definition: Roche lobe
related: close binary star
related: eclipsing binary star
related: interacting binary star
related: tidal interaction

rocket-borne instrument
type: Concept
alternative label: rocket borne instrument
definition: rocket-borne instrument
related: X-ray astronomy
related: airplane-borne instrument
related: balloon-borne instrument
related: cosmic ray astronomy
related: gamma-ray astronomy
related: ground-based astronomy
related: infrared observatory
related: satellite-borne instrument
related: space probe instrument
related: space telescope
related: ultraviolet astronomy

roentgenium
type: Concept
alternative label: Rg
broader: fundamental chemical element
definition: roentgenium (atomic number 111)
history note: FVH: new (2007-OCT-25)

Rosseland opacity
type: Concept
broader: opacity
definition: Rosseland opacity
related: Kramers opacity
related: absorption
related: stellar interior

rotating body
type: Concept
definition: rotating body
narrower: asteroid
narrower: circumstellar disk
narrower: comet
narrower: dwarf planet
narrower: galaxy
narrower: planet
narrower: rotating star
related: rigid body rotation
related: rotation

rotating shell
type: Concept
broader: circumstellar shell
definition: rotating shell

rotating star
type: Concept
broader: rotating body
definition: rotating star
narrower: periodic variable star
related: radiative braking
related: synchronous rotation
related: von Zeipel theorem

rotational velocity
type: Concept
broader: velocity
definition: rotational velocity
history note: ES: new (2007-OCT-11)
related: rotation
related: tangential velocity

rotation
type: Concept
definition: rotation
narrower: Earth rotation
narrower: Galactic rotation
narrower: differential rotation
narrower: galaxy rotation curve
narrower: rigid body rotation
narrower: synchronous rotation
related: angular momentum
related: angular velocity
related: equatorial bulge
related: oblateness
related: period
related: rotating body
related: rotational velocity
scope note: combine with other terms

r-process
type: Concept
alternative label: r process
definition: r-process
related: nucleosynthesis
related: p process
related: s-process
related: supernova

RRab star
type: Concept
broader: RR Lyrae star
definition: RRab star

RRa star
type: Concept
broader: RR Lyrae star
definition: RRa star

RRb star
type: Concept
broader: RR Lyrae star
definition: RRb star

RRc star
type: Concept
broader: RR Lyrae star
definition: RRc star

RR Lyrae star
type: Concept
alternative label: cluster type variable star
broader: double-mode variable star
broader: population II Cepheid
broader: pulsating variable star
definition: RR Lyrae star
narrower: Bailey type
narrower: RRa star
narrower: RRab star
narrower: RRb star
narrower: RRc star
related: BL Herculis star
related: Blazhko effect
related: Cepheid
related: Galactic halo
related: Oosterhoff group
related: W Virginis star
related: globular star cluster
related: horizontal branch star

RR Telescopii star
type: Concept
definition: RR Telescopii star

RS Canum Venaticorum star
type: Concept
broader: X-ray source
broader: binary star
broader: multi-periodic variable star
definition: RS Canum Venaticorum star
related: starspot

R star
type: Concept
broader: giant
broader: late-type star
definition: R star
related: carbon star
related: spectral type

rubidium
type: Concept
alternative label: Rb
broader: fundamental chemical element
definition: rubidium (atomic number 37)
history note: FVH: new (2007-OCT-25)

runaway star
type: Concept
definition: runaway star
related: OB star
related: binary star
related: high-velocity star
related: supernova

ruthenium
type: Concept
alternative label: Ru
broader: fundamental chemical element
definition: ruthenium (atomic number 44)
history note: FVH: new (2007-OCT-25)

rutherfordium
type: Concept
alternative label: Rf
broader: fundamental chemical element
definition: rutherfordium (atomic number 104)
history note: FVH: new (2007-OCT-25)

RV Tauri star
type: Concept
broader: emission line star
broader: irregular variable star
broader: late-type supergiant
broader: long period variable star
broader: pulsating variable star
broader: semi-regular variable star
definition: RV Tauri star
related: S Vulpeculae star
related: radial pulsation

RW Aurigae star
type: Concept
broader: emission line star
broader: irregular variable star
broader: pre-main sequence star
broader: ultraviolet excess star
definition: RW Aurigae star
related: H alpha emission line star
related: T association
related: T Tauri star

Saha equation
type: Concept
definition: Saha equation
related: ion
related: thermal equilibrium

samarium
type: Concept
alternative label: Sm
broader: fundamental chemical element
broader: rare earth
definition: samarium (atomic number 62)
history note: FVH: new (2007-OCT-25)

sampling
type: Concept
definition: sampling
scope note: combine with other terms

Saros cycle
type: Concept
definition: Saros cycle
related: lunar eclipse
related: lunar phase
related: metonic cycle

satellite-borne instrument
type: Concept
alternative label: satellite borne instrument
definition: satellite-borne instrument
related: X-ray astronomy
related: airplane-borne instrument
related: balloon-borne instrument
related: cosmic ray astronomy
related: gamma-ray astronomy
related: ground-based astronomy
related: infrared astronomy
related: millimeter astronomy
related: rocket-borne instrument
related: space probe instrument
related: space telescope
related: ultraviolet astronomy

satellite laser ranging
type: Concept
broader: laser ranging
definition: satellite laser ranging
related: artificial satellite
related: laser
related: lunar laser ranging
related: optical radar

satellite
type: Concept
definition: satellite
narrower: Moon
narrower: galilean satellite
narrower: planet satellite
related: Solar System
related: global positioning system
related: planet
related: planetesimal
related: protoplanet
related: rill
related: surface of celestial body
related: topography
related: volcano
scope note: natural satellite; see artifical_satellite

Saturn
type: Concept
broader: Jovian planet
broader: planet
definition: Saturn
history note: FVH: new (2007-SEP-24)
related: Solar System

SBF distance
type: Concept
alternative label: SBF
broader: distance measurement
definition: surface brightness fluctuation distance
history note: ES: new (2007-OCT-8)
related: elliptical galaxy

scale height
type: Concept
definition: scale height
related: Earth atmosphere
related: atmosphere
related: atmospheric density
related: stellar atmosphere

scandium
type: Concept
alternative label: Sc
broader: fundamental chemical element
broader: rare earth
definition: scandium (atomic number 21)
history note: FVH: new (2007-OCT-25)

scattering
type: Concept
definition: scattering
narrower: Compton scattering
narrower: Mie scattering
narrower: atmospheric extinction
narrower: elementary particle scattering
narrower: gamma-ray scattering
narrower: light scattering
related: radiation scattering
related: reflection
related: refraction

Schmidt camera
type: Concept
broader: camera
broader: photographic instrument
definition: Schmidt camera
related: Schmidt telescope
related: corrector plate

Schmidt telescope
type: Concept
broader: catadioptric system
broader: photographic instrument
broader: reflecting telescope
definition: Schmidt telescope
related: Baker-Nunn camera
related: Maksutov telescope
related: Schmidt camera
related: corrector plate
related: objective prism
related: wide-field telescope

Schwarzschild metric
type: Concept
definition: Schwarzschild metric
related: general theory of relativity
related: gravitational field
related: ionization
related: orbit
related: space-time singularity

Schwarzschild radius
type: Concept
definition: Schwarzschild radius
related: black hole
related: general theory of relativity
scope note: limiting radius of black hole

scientific field
type: Concept
definition: scientific and related field
narrower: Earth sciences
narrower: aeronomy
narrower: astrobiology
narrower: astrology
narrower: astronomy
narrower: astrophysics
narrower: atomic physics
narrower: biology
narrower: celestial mechanics
narrower: chemistry
narrower: engineering
narrower: fluid mechanics
narrower: mathematics

scintillation counter
type: Concept
broader: counter
definition: scintillation counter
narrower: Cerenkov counter
related: image tube
related: phosphorescence
related: phosphorescent scintillation
related: photomultiplier tube

scintillation
type: Concept
definition: scintillation
narrower: atmospheric scintillation
narrower: interplanetary scintillation
narrower: interstellar scintillation
narrower: ionospheric scintillation
narrower: phosphorescent scintillation
related: Earth
related: Earth atmosphere
related: atmosphere
related: atmospheric refraction
related: speckle
related: turbulence Earth atmosphere

S Doradus star
type: Concept
alternative label: P Cygni star
broader: early-type variable star
broader: emission line star
broader: shell star
definition: S Doradus star
related: P Cygni line profile

seaborgium
type: Concept
alternative label: Sg
broader: fundamental chemical element
definition: seaborgium (atomic number 106)
history note: FVH: new (2007-OCT-25)

search for extraterrestrial life
type: Concept
alternative label: SETI
change note: FVH: added RT EXTRATERRESTRIAL_INTELLIGENCE (2007-OCT-1)
change note: FVH: explicit wording of token; SETI to ALT (2007-OCT-4)
definition: search for extraterrestrial life
related: extraterrestrial intelligence
related: extraterrestrial life

seasonal phenomena
type: Concept
definition: seasonal phenomena
scope note: combine with other terms

season
type: Concept
definition: season
scope note: combine with other terms

secondary cosmic ray
type: Concept
definition: secondary cosmic ray
related: cosmic ray
related: cosmic ray shower

secondary mirror
type: Concept
broader: telescope mirror
definition: secondary mirror
related: Cassegrain antenna
related: Cassegrain focus
related: optical telescope
related: primary mirror
related: reflecting telescope
related: subreflector
related: tertiary mirror

secondary star
type: Concept
broader: companion star
definition: secondary star
history note: ES: new (2007-OCT-8)
related: primary star
related: tertiary star

secular parallax
type: Concept
broader: parallax
definition: secular parallax
related: moving cluster parallax
related: proper motion
related: star association

seeing monitor
type: Concept
broader: optical instrument
definition: seeing monitor
narrower: differential image motion monitor
related: optical observatory
related: seeing
related: site testing

seeing
type: Concept
definition: seeing
narrower: dome seeing
related: Earth atmosphere
related: active optics
related: adaptive optics
related: atmospheric refraction
related: atmospheric scintillation
related: point spread function
related: seeing monitor
related: site testing
related: speckle
related: speckle interferometry
related: tip-tilt mirror
related: turbulence Earth atmosphere

segmented optics
type: Concept
definition: segmented optics
related: adaptive optics
related: multiple mirror telescope
related: tip-tilt mirror
related: very large telescope

seismology
type: Concept
definition: seismology
narrower: asteroseismology
narrower: helioseismology
related: Earth
related: stellar oscillation
related: vibration

selection effect
type: Concept
broader: error
definition: selection effect
related: correction
related: statistics
scope note: combine with other terms

selective absorption
type: Concept
definition: selective absorption
related: gas to dust ratio
related: interstellar matter
related: interstellar reddening
related: reddening
related: reddening law

selenium
type: Concept
alternative label: Se
broader: fundamental chemical element
definition: selenium (atomic number 34)
history note: FVH: new (2007-OCT-25)

selenology
type: Concept
definition: selenology
related: Moon

self-absorption
type: Concept
alternative label: self absorption
definition: self-absorption
related: spectrum

self-calibration method
type: Concept
alternative label: self calibration method
broader: calibration
definition: self-calibration method

semi-barium star
type: Concept
alternative label: semibarium star
broader: barium star
definition: semi-barium star

semiconductor device
type: Concept
definition: semiconductor device
narrower: charge-coupled device
narrower: charge-injection device
narrower: charge-transfer device
narrower: photovoltaic cell
related: Gunn diode
related: detector

semi-detached binary star
type: Concept
alternative label: semidetached binary star
broader: binary star
broader: close binary star
definition: semi-detached binary star
related: detached binary star

semimajor axis
type: Concept
alternative label: semi-major axis
broader: orbital element
definition: semimajor axis
narrower: major axis
related: binary star
related: planet

semiminor axis
type: Concept
alternative label: semi-minor axis
definition: semiminor axis
narrower: minor axis

semi-regular variable star
type: Concept
alternative label: semiregular variable star
broader: late-type giant
broader: pulsating variable star
broader: variable star
definition: semi-regular variable star
narrower: RV Tauri star
narrower: S Vulpeculae star
related: Mira variable star
related: irregular variable star
related: supergiant

sensitivity
type: Concept
definition: sensitivity
related: detector
related: integration time
related: limiting magnitude
related: polar diagram
related: precision
related: resolution
related: signal detection
related: signal-to-noise ratio

sensitometer
type: Concept
broader: measuring instrument
definition: sensitometer

separation
type: Concept
definition: separation
related: binary star
related: occulting disk
related: visual binary star
scope note: combine with other terms

sextant
type: Concept
broader: astrometric instrument
broader: instrument
definition: sextant
related: altitude angle

Seyfert galaxy
type: Concept
broader: peculiar galaxy
definition: Seyfert galaxy
related: BL Lacertae object
related: Markarian galaxy
related: Seyfert nucleus
related: X-ray source
related: compact nucleus
related: emission line galaxy
related: liner galaxy
related: massive object

Seyfert nucleus
type: Concept
broader: active galactic nucleus
broader: compact nucleus
broader: emission line galaxy
definition: Seyfert nucleus
related: Seyfert galaxy

S galaxy
type: Concept
broader: spiral galaxy
definition: spiral galaxy (Yerkes classification scheme)
history note: FVH: new (2007-OCT-12)
related: Yerkes classification

shadow band
type: Concept
definition: shadow band
related: diffraction
related: interference wave
related: solar eclipse

shaped reflector
type: Concept
definition: shaped reflector
related: radio telescope

shell burning
type: Concept
definition: shell burning
related: carbon burning
related: helium burning
related: hydrogen burning
related: nuclear fusion
scope note: nuclear fusion in shell

shell
type: Concept
definition: shell
narrower: circumstellar shell
narrower: convective shell
narrower: dust shell
related: shell star

shell star
type: Concept
definition: shell star
narrower: S Doradus star
narrower: Z Andromedae star
narrower: gamma Cassiopeiae star
related: P Cygni line profile
related: circumstellar shell
related: shell
scope note: ES: deleted BT emission_line_star (2007-OCT-8)

shepherd satellite
type: Concept
definition: shepherd satellite
related: planetary ring
related: resonance gap

shock
type: Concept
definition: shock
related: collisional plasma
related: ionization
related: stellar wind
related: supernova
scope note: combine with other terms

shock wave
type: Concept
definition: shock wave
narrower: bow shock
narrower: ionizing shock wave
related: Rankine-Hugoniot relation
related: jump condition
related: sound speed
related: supernova envelope
related: velocity field
related: wave propagation

short period variable star
type: Concept
definition: short period variable star
narrower: beta Cephei star
narrower: delta Scuti star

shot noise
type: Concept
broader: noise
definition: shot noise
related: detector
related: electronic equipment

shutter
type: Concept
definition: shutter
history note: FVH: new (2007-SEP-21)
related: camera
related: detector

sidelobe
type: Concept
alternative label: lobe [telescope beam]
definition: sidelobe
related: polar diagram
related: radio antenna
related: resolution

sidereal time
type: Concept
alternative label: S.T.
broader: time
definition: sidereal time
related: Earth
related: civil time
related: equation of the equinox
related: hour angle
related: transit time
related: year

siderostat
type: Concept
definition: siderostat
related: altazimuth mounting
related: coelostat
related: drive
related: heliostat
related: telescope mounting

sigma8
type: Concept
alternative label: sigma_8
broader: cosmological parameter
definition: the normalization factor of the cosmological matter power spectrum
history note: FVH: new (2007-OCT-24)

signal analysis
type: Concept
broader: analysis
definition: signal analysis
related: signal detection
related: signal processing

signal detection
type: Concept
broader: detection
definition: signal detection
related: detector
related: limiting magnitude
related: sensitivity
related: signal analysis
related: signal processing

signal processing
type: Concept
broader: analysis
definition: signal processing
related: signal analysis
related: signal detection

signal-to-noise ratio
type: Concept
alternative label: SNR
alternative label: signal to noise ratio
definition: signal to noise ratio
related: background noise
related: integration time
related: limiting magnitude
related: noise
related: sensitivity
related: sky noise

silicon burning
type: Concept
broader: nuclear fusion
broader: nucleosynthesis
definition: silicon burning
related: carbon burning
related: helium burning
related: hydrogen burning
related: silicon

silicon monoxide
type: Concept
alternative label: SiO
change note: FVH: explicit wording of token (2007-OCT-4)
definition: SiO molecule
history note: FVH: new (2007-OCT-2)
related: SiO maser
related: silicon

silicon
type: Concept
alternative label: Si
broader: fundamental chemical element
definition: silicon (atomic number 14)
history note: FVH: new (2007-OCT-25)
related: silicon burning
related: silicon monoxide
related: silicon star

silicon star
type: Concept
broader: Ap star
broader: metal-rich star
definition: silicon star
related: silicon

silver coating
type: Concept
broader: coating
broader: thin film
definition: silver coating
related: aluminum coating
related: optical surface
related: silver

silver
type: Concept
alternative label: Ag
broader: fundamental chemical element
definition: silver (atomic number 47)
history note: FVH: new (2007-OCT-25)
related: silver coating

simulation
type: Concept
definition: simulation
narrower: computer simulation
related: model

singularity
type: Concept
definition: singularity
narrower: naked singularity
narrower: space-time singularity

SiO maser
type: Concept
broader: maser
definition: SiO maser
related: OH maser
related: interstellar matter
related: radio source
related: silicon monoxide
related: water maser

site protection
type: Concept
definition: site protection
related: air pollution
related: light pollution
related: observatory

site testing
type: Concept
definition: site testing
related: observatory
related: pollution
related: seeing
related: seeing monitor
related: sky brightness

sky brightness
type: Concept
definition: sky brightness
narrower: night sky brightness
related: Milky Way galaxy
related: airglow
related: atmospheric radiation
related: aurora
related: background radiation
related: site testing
related: sunlight
related: twilight
related: zodiacal light

sky noise
type: Concept
broader: noise
definition: sky noise
related: background noise
related: signal-to-noise ratio

sky
type: Concept
definition: sky
scope note: combine with other terms

sky survey
type: Concept
broader: survey
definition: sky survey
related: atlas
related: catalog
related: finding chart
related: map

slit mask
type: Concept
broader: spectrograph slit
definition: slit mask
history note: FVH: new (2007-OCT-3)

Sloan photometry
type: Concept
alternative label: SDSS photometry
broader: broad band photometry
broader: photometric system
definition: Sloan photometry
history note: FVH: new (2007-SEP-21)
related: two-color photometry

slow nova
type: Concept
alternative label: novoid
broader: nova
definition: slow nova
narrower: DQ Herculis star
related: fast nova
related: recurrent nova

Small Magellanic Cloud
type: Concept
alternative label: SMC
broader: Magellanic cloud
definition: Small Magellanic Cloud
related: Large Magellanic Cloud

sodium
type: Concept
alternative label: Na
broader: fundamental chemical element
definition: sodium (atomic number 11)
history note: FVH: new (2007-OCT-25)

soft gamma-ray repeater
type: Concept
broader: gamma-ray source
broader: irregular variable star
broader: magnetar
definition: soft gamma-ray repeater
history note: ES: new (2007-OCT-8)

solar activity
type: Concept
definition: solar activity
narrower: solar storm
related: Maunder minimum
related: active Sun
related: activity index
related: aurora
related: butterfly diagram
related: coronal loop
related: emerging flux
related: ephemeral active region
related: flare
related: heliosphere
related: magnetic storm
related: prominence
related: solar atmosphere
related: solar cycle
related: solar wind
related: sunspot
related: sunspot cycle
related: sunspot group
related: sunspot number

solar atmosphere
type: Concept
broader: stellar atmosphere
definition: solar atmosphere
related: chromosphere
related: heliopause
related: heliosphere
related: limb darkening
related: line formation
related: solar activity
related: solar corona
related: solar physics
related: solar storm
related: solar surface
related: solar-terrestrial relation
related: solar wind

solar constant
type: Concept
definition: solar constant
related: Sun
related: electromagnetic radiation
related: radiation
related: solar physics
related: sunlight

solar corona
type: Concept
broader: corona
definition: solar corona
narrower: m region
related: K corona
related: Sun
related: coronagraph
related: coronal dimming
related: coronal hole
related: coronal line
related: coronal loop
related: coronal mass ejection
related: coronal plume
related: coronal transient
related: coronal wave
related: solar atmosphere
related: transition region

solar cycle
type: Concept
definition: solar cycle
related: active Sun
related: butterfly diagram
related: quiet Sun
related: solar activity
related: solar physics
related: sunspot cycle
related: sunspot number

solar day
type: Concept
definition: solar day
related: Universal Time
related: ephemeris time

solar eclipse
type: Concept
broader: eclipse
definition: solar eclipse
related: Moon
related: Sun
related: bailys bead
related: diamond ring effect
related: flash spectrum
related: penumbra
related: shadow band
related: umbra
related: zone of totality

solar filament
type: Concept
definition: solar filament
related: Sun
related: chromosphere
related: flare
related: prominence
related: sunspot

solar interior
type: Concept
broader: stellar interior
definition: solar interior
related: solar neutrino problem
related: solar physics
related: stellar evolution
related: stellar structure

solar motion
type: Concept
broader: motion
definition: solar motion
related: antapex
related: apex
scope note: with respect to nearby star

solar nebula
type: Concept
definition: solar nebula
related: Solar System
related: planet
related: protoplanet
related: protoplanetary nebula

solar neutrino problem
type: Concept
definition: solar neutrino problem
related: neutrino
related: nuclear reaction
related: solar interior

solar observatory
type: Concept
definition: solar observatory
related: coronagraph
related: solar optical telescope
related: solar radio telescope
related: solar telescope

solar optical telescope
type: Concept
broader: solar telescope
definition: solar optical telescope
related: solar observatory
related: solar radio telescope

solar oscillation
type: Concept
alternative label: five minute oscillation
broader: stellar oscillation
definition: solar oscillation
related: asteroseismology
related: helioseismology

solar parallax
type: Concept
definition: solar parallax
related: Astronomical Unit
related: Earth orbit

solar physics
type: Concept
definition: solar physics
related: Sun
related: forbush effect
related: solar atmosphere
related: solar constant
related: solar cycle
related: solar interior
related: solar telescope
related: solar-terrestrial relation

solar-planetary relation
type: Concept
alternative label: solar planetary relation
definition: solar-planetary relation
narrower: solar-terrestrial relation
related: Solar System
related: Sun
related: planet

solar radio telescope
type: Concept
broader: solar telescope
definition: solar radio telescope
related: solar observatory
related: solar optical telescope

solar
type: Concept
definition: solar
scope note: see under Sun

solar storm
type: Concept
broader: solar activity
definition: solar storm
related: solar atmosphere

solar surface
type: Concept
definition: solar surface
related: Sun
related: photosphere
related: solar atmosphere
related: supergranulation

Solar System
type: Concept
broader: planetary system
definition: Solar System
related: Bodes law
related: Ceres
related: Earth
related: Earth-Moon system
related: Edgeworth-Kuiper belt
related: Jupiter
related: Kreutz sungrazer
related: Mars
related: Mercury
related: Neptune
related: Pluto
related: Saturn
related: Sun
related: Uranus
related: Venus
related: asteroid
related: comet
related: extrasolar planet
related: origin
related: planet
related: planetary alignment
related: planetary theory
related: planetesimal
related: pre-solar nebula
related: protoplanet
related: satellite
related: solar nebula
related: solar-planetary relation
related: synodic period
related: trans-Neptunian object
related: transplutonian planet
scope note: not a complete list of terms

solar telescope
type: Concept
alternative label: tower telescope
broader: telescope
definition: solar telescope
narrower: radioheliograph
narrower: solar optical telescope
narrower: solar radio telescope
related: heliostat
related: solar observatory
related: solar physics

solar-terrestrial relation
type: Concept
alternative label: solar terrestiral relation
broader: solar-planetary relation
definition: solar-terrestrial relation
related: Earth
related: Sun
related: solar atmosphere
related: solar physics

solar wind
type: Concept
broader: interplanetary matter
broader: plasma
broader: stellar wind
definition: solar wind
related: Poynting-Robertson effect
related: coronal hole
related: heliopause
related: heliosphere
related: interplanetary gas
related: interstellar wind
related: radiation pressure
related: solar activity
related: solar atmosphere

solstice
type: Concept
definition: solstice
narrower: summer solstice
narrower: winter solstice
related: Tropic of Cancer
related: Tropic of Capricorn
related: ecliptic
related: equinox

sound speed
type: Concept
alternative label: speed of sound
definition: speed of sound
related: acoustic wave
related: shock wave

source
type: Concept
definition: astronomical source
history note: FVH: new (2007-NOV-4)
narrower: X-ray source
narrower: compact source
narrower: cosmic ray source
narrower: extended source
narrower: field star
narrower: gamma-ray source
narrower: gravitationally lensed source
narrower: infrared source
narrower: non-thermal source
narrower: radio source
narrower: variable source

South Celestial Pole
type: Concept
alternative label: S.C.P.
alternative label: SCP
broader: celestial pole
definition: South Celestial Pole
related: North Celestial Pole

South Ecliptic Pole
type: Concept
alternative label: S.E.P.
alternative label: SEP
broader: ecliptic pole
definition: South Ecliptic Pole
related: North Ecliptic Pole

southern hemisphere
type: Concept
definition: southern hemisphere
related: northern hemisphere

South Galactic Pole
type: Concept
alternative label: S.G.P.
alternative label: SGP
broader: Galactic pole
definition: South Galactic Pole
related: North Galactic Pole

space astrometry
type: Concept
broader: astrometry
definition: space astrometry
related: space geodesy
related: space observatory

space astronomy
type: Concept
broader: astronomy
definition: space astronomy
narrower: X-ray astronomy
narrower: gamma-ray astronomy
narrower: ultraviolet astronomy
related: artificial satellite
related: space exploration
related: space observatory
related: space probe

space biology
type: Concept
broader: biology
broader: space research
definition: space biology
related: space observatory
related: space vehicle

space debris
type: Concept
alternative label: debris
broader: space vehicle
definition: space debris
related: space law
related: space pollution

space exploration
type: Concept
definition: space exploration
related: discoveries
related: interstellar communication
related: planet
related: space astronomy
related: space observatory
related: space probe
related: space research
related: space telescope
related: space vehicle

space geodesy
type: Concept
broader: geodesy
definition: space geodesy
related: Earth
related: space astrometry
related: space observatory

space law
type: Concept
definition: space law
related: space debris
related: space research

space motion
type: Concept
broader: motion
definition: space motion
narrower: proper motion
narrower: radial velocity
related: Galactic rotation
related: stellar motion
related: transverse velocity

space observatory
type: Concept
alternative label: orbiting observatory
broader: artificial satellite
broader: observatory
change note: FVH: merged with orbiting_observatory (2007-NOV-15)
definition: space observatory
narrower: Hubble Space Telescope
narrower: IRAS satellite
narrower: X-ray observatory
narrower: gamma-ray observatory
related: X-ray astronomy
related: infrared observatory
related: space astrometry
related: space astronomy
related: space biology
related: space exploration
related: space geodesy
related: space probe
related: space research
related: space telescope
related: ultraviolet astronomy

space pollution
type: Concept
broader: pollution
definition: space pollution
related: space debris

space probe instrument
type: Concept
definition: space probe instrument
narrower: space telescope
related: balloon-borne instrument
related: ground-based astronomy
related: rocket-borne instrument
related: satellite-borne instrument
related: space probe

space probe
type: Concept
alternative label: probe
definition: space probe
related: space astronomy
related: space exploration
related: space observatory
related: space probe instrument
related: space vehicle

space research
type: Concept
alternative label: space science
broader: astronomical research
definition: space research
narrower: space biology
related: space exploration
related: space law
related: space observatory

space
type: Concept
definition: space
related: general theory of relativity
related: special theory of relativity
related: vacuum

space telescope
type: Concept
broader: space probe instrument
broader: telescope
definition: space telescope
narrower: X-ray telescope
narrower: gamma-ray telescope
narrower: ultraviolet telescope
related: artificial satellite
related: balloon-borne instrument
related: ground-based astronomy
related: rocket-borne instrument
related: satellite-borne instrument
related: space exploration
related: space observatory
scope note: named telescope not included

space-time curvature
type: Concept
definition: curvature of space-time
related: Dark Energy
related: cosmology
related: general theory of relativity

space-time singularity
type: Concept
broader: singularity
definition: space-time singularity
related: Schwarzschild metric
related: black hole
related: naked singularity
related: quantum cosmology

space vehicle
type: Concept
definition: space vehicle
narrower: space debris
related: artificial satellite
related: space biology
related: space exploration
related: space probe
scope note: named vehicles not included

special theory of relativity
type: Concept
broader: general theory of relativity
definition: special theory of relativity
related: space

speckle interferometry
type: Concept
broader: interferometry
definition: speckle interferometry
related: angular diameter
related: angular resolution
related: angular separation
related: seeing
related: speckle

speckle
type: Concept
definition: speckle
related: atmospheric refraction
related: scintillation
related: seeing
related: speckle interferometry

spectral band
type: Concept
definition: spectral band
narrower: molecular band
related: molecular line
related: molecular spectrum
related: telluric line

spectral classification
type: Concept
broader: classification
definition: spectral classification
narrower: Henry Draper system
narrower: MK classification
related: Henry Draper catalog
related: luminosity classification
related: spectral type

spectral index
type: Concept
definition: spectral index
related: radio frequency
related: radio spectrum

spectral line
type: Concept
alternative label: spectrum line
definition: spectral line
narrower: D line
narrower: Fraunhofer line
narrower: absorption line
narrower: calcium line
narrower: carbon line
narrower: cyanogen line
narrower: emission line
narrower: hyperfine line
narrower: metal line
narrower: molecular line
narrower: technetium line
narrower: telluric line
narrower: ultraviolet line
related: equivalent width
related: fine structure
related: instrumental profile
related: line blanketing
related: line blending
related: line broadening
related: line formation
related: line identification
related: line intensitite
related: line profile
related: line ratio
related: natural line broadening
related: natural line width
related: spectral type
related: transition probability
scope note: not a complete list of terms

spectral resolution
type: Concept
broader: resolution
definition: spectral resolution
related: line blending

spectral type
type: Concept
definition: spectral type
related: A star
related: B star
related: F star
related: G star
related: K star
related: L dwarf
related: M star
related: N star
related: O star
related: R star
related: S star
related: T dwarf
related: line width
related: luminosity class
related: luminosity classification
related: spectral classification
related: spectral line
related: standard star
related: temperature
scope note: not a complete list of terms

spectrograph slit
type: Concept
alternative label: slit
definition: spectrograph slit
history note: FVH: new (2007-SEP-21)
narrower: long slit
narrower: slit mask
related: long slit spectrum
related: multi-slit spectrograph
related: spectrograph
related: three-dimensional spectrum
related: two-dimensional spectrum

spectrograph
type: Concept
broader: instrument
broader: optical instrument
broader: telescope instrument
change note: FVH: added RT SPECTROGRAPH_SLITS, NT INTEGRAL_FIELD_SPECTROGRAPHS, MULTI_FIBER_SPECTROGRAPHS, and MULTI_SLIT_SPECTROGRAPHS (2007-SEP-21)
definition: spectrograph
narrower: Coude spectrograph
narrower: Fabry-Perot spectrograph
narrower: Fourier spectrograph
narrower: X-ray spectrograph
narrower: echelle spectrograph
narrower: gamma-ray spectrograph
narrower: grating spectrograph
narrower: grazing incidence spectrograph
narrower: integral field spectrograph
narrower: multi-channel spectrograph
narrower: multi-fiber spectrograph
narrower: multi-slit spectrograph
narrower: optical spectrograph
narrower: prism spectrograph
narrower: radio spectrograph
narrower: ultraviolet spectrograph
related: VPH grating
related: comparison lamp
related: diffraction grating
related: echelle grating
related: flat field lamp
related: grism
related: prism
related: spectrograph slit
related: spectroheliograph
related: spectroscopy

spectrography
type: Concept
alternative label: spectrophotography
broader: photography
broader: spectroscopy
definition: spectrography
scope note: see spectroscopy

spectroheliograph
type: Concept
definition: spectroheliograph
related: coronagraph
related: photoheliograph
related: spectrograph

spectrophotometer
type: Concept
broader: photometer
definition: spectrophotometer
related: spectrophotometry
related: telescope instrument

spectrophotometry
type: Concept
broader: astronomical technique
broader: observing technique
definition: spectrophotometry
related: color
related: optical scanners
related: photometry
related: spectrophotometer
related: spectroscopy
related: standard candle

spectroscopic analysis
type: Concept
alternative label: spectral analysis
definition: spectroscopic analysis
related: Doppler effect
related: Milne Eddington approximation
related: absorption line
related: collision broadening
related: continuous spectrum
related: emission line
related: maximum entropy method
related: spectrum
related: wave motion
related: waveform analysis

spectroscopic binary star
type: Concept
alternative label: spectrum binary star
broader: binary star
definition: spectroscopic binary star
narrower: two-spectrum binary star
related: Doppler effect
related: eclipsing binary star
related: ellipsoidal variable star
related: mass
related: mass function
related: velocity curve

spectroscopy
type: Concept
alternative label: spectrometry
broader: astronomical technique
broader: observing technique
definition: spectroscopy
narrower: Fourier transform spectroscopy
narrower: Raman spectroscopy
narrower: X-ray spectroscopy
narrower: absorption spectroscopy
narrower: collision spectroscopy
narrower: gamma-ray spectroscopy
narrower: high-resolution spectrosopy
narrower: interference spectrosocopy
narrower: microwave spectroscopy
narrower: optical spectroscopy
narrower: spectrography
narrower: three-dimensional spectroscopy
narrower: time-resolved spectroscopy
narrower: two-dimensional spectroscopy
related: collisional excitation
related: continuous spectrum
related: heterodyne
related: pressure broadening
related: radial velocity
related: reseaux
related: spectrograph
related: spectrophotometry
related: spectrum
scope note: not a complete list of terms

spectrum
type: Concept
definition: spectrum
narrower: abnormal spectrum
narrower: absorption spectrum
narrower: atomic spectrum
narrower: brillouin spectrum
narrower: continuous spectrum
narrower: echelle spectrum
narrower: emission spectrum
narrower: hydrogen spectrum
narrower: microwave spectrum
narrower: molecular spectrum
narrower: radio spectrum
narrower: three-dimensional spectrum
narrower: two-dimensional spectrum
narrower: vibrational spectrum
narrower: visible spectrum
related: Hertzsprung-Russell diagram
related: MK classification
related: absorption line
related: bremsstrahlung
related: contiuum
related: diffraction grating
related: emission line
related: energy level
related: equivalent width
related: fluorescence
related: forbidden line
related: forbidden transition
related: free-free emission
related: hyperfine line
related: prism
related: recombination line
related: resonance line
related: self-absorption
related: spectroscopic analysis
related: spectroscopy
related: stimulated emission
scope note: not a complete list of terms

spectrum variable star
type: Concept
broader: Am star
broader: Ap star
broader: intrinsic variable star
definition: spectrum variable star
narrower: manganese star
related: alpha2 Canum Venaticorum star
related: magnetic star
related: oblique rotator

spherical aberration
type: Concept
broader: optical aberration
definition: spherical aberration
related: astigmatism
related: chromatic aberration
related: comatic aberration
related: distortion
related: field curvature

spherical coordinate
type: Concept
alternative label: angular coordinate
definition: spherical coordinate
related: coordinate system
related: position
related: reference system

SPH simulation
type: Concept
alternative label: SPH
alternative label: smoothed-particle hydrodynamics
broader: numerical simulation
definition: SPH simulation
history note: FVH: new (2007-OCT-3)

spicule
type: Concept
definition: spicule
narrower: macro spicule
related: Sun
related: chromosphere

spiral arm
type: Concept
alternative label: arm
definition: spiral arm
related: Galactic structure
related: galaxy structure
related: gas distribution
related: interstellar magnetic field
related: interstellar matter
related: open star cluster
related: pitch angle
related: population I star
related: spiral galaxy

spiral galaxy
type: Concept
broader: disk galaxy
broader: galaxy
definition: spiral galaxy
narrower: Milky Way galaxy
narrower: S galaxy
narrower: barred spiral galaxy
related: late-type galaxy
related: pitch angle
related: spiral arm

s-process
type: Concept
alternative label: s process
definition: s-process
related: nucleosynthesis
related: p process
related: r-process
related: supernova

S star
type: Concept
alternative label: Se star
broader: giant
broader: late-type star
definition: S star
related: barium star
related: carbon star
related: heavy metal star
related: spectral type
related: technetium star
related: zirconium star

stability
type: Concept
definition: stability
related: vibration
scope note: combine with other terms

standard candle
type: Concept
definition: standard candle
related: effective temperature
related: photometric standard star
related: photometry
related: spectrophotometry

standard epoch
type: Concept
definition: standard epoch
narrower: Besselian epoch
narrower: Julian epoch

standard star
type: Concept
definition: standard star
narrower: comparison star
narrower: photometric standard star
related: position
related: spectral type

star association
type: Concept
definition: star association
narrower: O association
narrower: OB association
narrower: R association
narrower: T association
related: Goulds belt
related: open star cluster
related: secular parallax

star atlas
type: Concept
broader: atlas
definition: star atlas
related: finding chart
related: map

starburst galaxy
type: Concept
broader: galaxy
definition: starburst galaxy
related: star formation
related: stellar evolution

star cluster
type: Concept
alternative label: cluster of star
broader: cluster
definition: star cluster
narrower: globular star cluster
narrower: open star cluster
related: Poincare theorem
related: clustering
related: initial mass function
related: integrated magnitude
related: luminosity function
related: mass function
related: protocluster
related: relaxation time
related: tidal disruption
related: tidal radius
related: velocity dispersion
related: velocity distribution
related: virial theorem

star count
type: Concept
definition: star count
related: Galactic structure
related: mass function
related: star distribution
related: statistics

star distribution
type: Concept
definition: star distribution
related: star count
related: survey

star formation
type: Concept
alternative label: formation of star
definition: star formation
related: Bok globule
related: Jeans length
related: birth rate
related: cometary globule
related: cooling flow
related: dark nebula
related: extrasolar planet
related: infrared source
related: pre-main sequence star
related: protostar
related: starburst galaxy
related: stellar evolution
related: stellar ring

Stark broadening
type: Concept
broader: line broadening
definition: Stark broadening
related: Doppler broadening
related: Zeeman splitting
related: natural line width

starspot
type: Concept
definition: starspot
narrower: sunspot
related: BY Draconis star
related: RS Canum Venaticorum star

star
type: Concept
broader: stellar object
definition: star
narrower: Sun
narrower: active star
narrower: barium star
narrower: binary star
narrower: bright star
narrower: central star
narrower: collapsed star
narrower: companion star
narrower: evolved star
narrower: faint star
narrower: field star
narrower: fundamental star
narrower: giant branch star
narrower: halo star
narrower: helium-poor star
narrower: helium-rich star
narrower: high-luminosity star
narrower: high-mass star
narrower: high-velocity star
narrower: hydrogen deficient star
narrower: hypergiant
narrower: intermediate population star
narrower: late-type star
narrower: lithium star
narrower: low-luminosity star
narrower: low-mass star
narrower: main sequence star
narrower: massive star
narrower: metal-deficient star
narrower: metal-poor star
narrower: metal-rich star
narrower: population I star
narrower: population II star
narrower: population III star
narrower: supernova
narrower: young star
scope note: combine star or stellar with other terms

statistical parallax
type: Concept
broader: parallax
definition: statistical parallax

statistical relation
type: Concept
definition: statistical relation
narrower: Faber-Jackson relation
narrower: Hubble diagram
narrower: Hubble law
narrower: Tully-Fisher relation
narrower: mass-luminosity relation
narrower: mass-radius relation
narrower: period-age relation
narrower: period-color relation
narrower: period-density relation
narrower: period-luminosity-color relation
narrower: period-luminosity relation
narrower: period-mass relation
narrower: period-radius relation
narrower: period-spectrum relation
narrower: radius-luminosity relation

statistics
type: Concept
definition: statistics
related: Monte Carlo technique
related: distribution function
related: radio source count
related: selection effect
related: star count
scope note: combine with other terms

steady-state theory
type: Concept
alternative label: steady state theory
broader: cosmology
definition: steady-state theory
related: Big Bang theory
related: closed universe
related: open universe

stellar atmosphere
type: Concept
broader: atmosphere
definition: stellar atmosphere
narrower: solar atmosphere
related: chromosphere
related: corona
related: dredge up
related: limb brightening
related: limb darkening
related: line broadening
related: line formation
related: line width
related: negative H ion
related: scale height
related: stellar structure
related: stellar wind
related: turbulence star atmosphere

stellar black hole
type: Concept
broader: black hole
broader: collapsed star
broader: stellar object
definition: stellar black hole
related: hypernova
related: stellar evolution

stellar dynamics
type: Concept
definition: stellar dynamics
related: Fokker-Planck equation
related: Galactic rotation
related: N-body problem
related: Poincare theorem
related: close encounter
related: encounter
related: galaxy rotation curve
related: proper motion
related: radial velocity
related: relaxation time
related: stellar motion
related: three-body problem
related: two-body problem

stellar evolution
type: Concept
broader: evolution
change note: FVH: moved STAR_ORIGIN to RT (2007-OCT-1)
definition: stellar evolution
related: Henyey track
related: Hertzsprung-Russell diagram
related: Kerr black hole
related: birth rate
related: carbon burning
related: chemical evolution
related: collapsed star
related: cosmology
related: e-process
related: evolutionary track
related: funneling
related: giant
related: gravitational equilibrium
related: helium burning
related: hydrogen burning
related: initial mass function
related: inner core
related: instability strip
related: luminosity function
related: mass-loss
related: protostar
related: solar interior
related: star formation
related: starburst galaxy
related: stellar black hole
related: stellar interior

stellar interior
type: Concept
definition: stellar interior
narrower: solar interior
related: Chandrasekhar mass
related: Chandrasekhar-Schoenberg limit
related: Eddington limit
related: Rosseland opacity
related: carbon burning
related: carbon nitrogen cycle
related: core
related: dredge up
related: gravity wave
related: helium burning
related: hydrogen burning
related: inner core
related: nuclear fusion
related: nucleosynthesis
related: oxygen burning
related: proton-proton reaction
related: stellar evolution
related: stellar structure
related: temperature zone

stellar motion
type: Concept
broader: motion
definition: stellar motion
related: Doppler effect
related: Local Standard of Rest
related: astrometry
related: peculiar motion
related: peculiar velocity
related: proper motion
related: radial velocity
related: space motion
related: stellar dynamics

stellar object
type: Concept
definition: star-like object, including star, brown dwarf, and evolved stellar core (NS, BH, WD)
history note: FVH+ES: new (2007-OCT)
narrower: black dwarf
narrower: brown dwarf
narrower: neutron star
narrower: planetar
narrower: star
narrower: stellar black hole
narrower: white dwarf

stellar oscillation
type: Concept
definition: stellar oscillation
narrower: solar oscillation
related: asteroseismology
related: seismology

stellar population
type: Concept
definition: stellar population
related: disk population
related: halo star
related: intermediate population star
related: population I star
related: population II star
related: population III star

stellar ring
type: Concept
broader: ring
definition: stellar ring
related: star formation

stellar
type: Concept
definition: stellar
scope note: see sn for star

stellar structure
type: Concept
definition: stellar structure
related: hydrostatic equilibrium
related: macroturbulence
related: model
related: polytrope
related: solar interior
related: stellar atmosphere
related: stellar interior

stellar wind
type: Concept
broader: mass-loss
broader: plasma
definition: stellar wind
narrower: solar wind
related: Poynting-Robertson effect
related: accretion disk
related: chromosphere
related: circumstellar shell
related: interstellar wind
related: radiation pressure
related: shock
related: stellar atmosphere

stimulated emission
type: Concept
definition: stimulated emission
related: laser
related: maser
related: population inversion
related: spectrum
related: stimulated radiation

stimulated radiation
type: Concept
definition: stimulated radiation
related: stimulated emission

stokes parameter
type: Concept
definition: Stokes parameter
related: light polarization
related: polarized radiation

stratopause
type: Concept
definition: stratopause
related: Earth atmosphere
related: mesosphere
related: stratosphere

stratosphere
type: Concept
definition: stratosphere
related: Earth atmosphere
related: stratopause
related: tropopause

streak photography
type: Concept
broader: photography
definition: streak photography

streamer
type: Concept
definition: streamer
related: comet
related: tail

stroboscope
type: Concept
broader: instrument
definition: stroboscope

Stromgren photometry
type: Concept
alternative label: Stromgren uvby system
alternative label: four-color photometry
alternative label: uvby system
broader: medium band photometry
broader: photometric system
definition: Stromgren photometry
related: H beta photometry
related: Kapteyn selected area
related: e region
related: f region

Stromgren sphere
type: Concept
broader: gaseous sphere
definition: Stromgren sphere
related: interstellar matter
related: ionization
related: ionized gas

strong gravitational lensing
type: Concept
broader: gravitational lensing
definition: strong gravitational lensing (resolved)
history note: FVH: new (2007-OCT-8)

strong interaction
type: Concept
broader: interaction
definition: strong interaction
related: nuclear physics
related: weak interaction
scope note: between atomic particle

strontium star
type: Concept
definition: strontium star
related: magnetic star
related: strontium

strontium
type: Concept
alternative label: Sr
broader: fundamental chemical element
definition: strontium (atomic number 38)
history note: FVH: new (2007-OCT-25)
related: strontium star

structure
type: Concept
definition: structure
narrower: galaxy structure
related: planet
scope note: combine with other terms

subdwarf
type: Concept
broader: subluminous star
definition: subdwarf star
narrower: A subdwarf
narrower: B subdwarf
narrower: F subdwarf
narrower: G subdwarf
narrower: K subdwarf
narrower: L subdwarf
narrower: M subdwarf
narrower: O subdwarf
narrower: T subdwarf
narrower: late-type subdwarf
related: Harman-Seaton sequence
related: dwarf

subgiant
type: Concept
broader: post-main sequence star
definition: subgiant star
narrower: A subgiant
narrower: F subgiant
narrower: G subgiant
narrower: K subgiant
narrower: M subgiant
related: luminosity classification

subluminous star
type: Concept
definition: subluminous star
narrower: degenerate star
narrower: subdwarf
related: population II star

submillimeter astronomy
type: Concept
broader: radio astronomy
definition: submillimeter astronomy
related: millimeter astronomy
related: radio observatory
related: submillimeter radiation

submillimeter radiation
type: Concept
alternative label: submillimeter wave
broader: electromagnetic radiation
change note: FVH: moved submillimeter_wave to here, cleaned up (2007-OCT-8)
definition: submillimeter radiation
related: submillimeter astronomy

subreflector
type: Concept
definition: subreflector
related: Cassegrain antenna
related: Cassegrain focus
related: radio telescope
related: secondary mirror
related: tertiary mirror

sulfur
type: Concept
alternative label: S
alternative label: sulphur
broader: fundamental chemical element
definition: sulfur (atomic number 16)
history note: FVH: new (2007-OCT-25)

summer solstice
type: Concept
broader: solstice
definition: summer solstice
related: Tropic of Cancer
related: winter solstice

Sun
type: Concept
broader: star
definition: Sun
narrower: active Sun
related: Fraunhofer line
related: Hanle effect
related: Local Standard of Rest
related: Solar System
related: active prominence
related: active region
related: bailys bead
related: bright point
related: chromosphere
related: diamond ring effect
related: flare
related: granulation
related: granule
related: lunar eclipse
related: macro spicule
related: mottle
related: photosphere
related: prominence
related: quiescent prominence
related: solar constant
related: solar corona
related: solar eclipse
related: solar filament
related: solar physics
related: solar-planetary relation
related: solar surface
related: solar-terrestrial relation
related: spicule
scope note: combine Sun or solar with other terms; not a complete list of terms

sunlight
type: Concept
definition: sunlight
related: sky brightness
related: solar constant
related: twilight

sunspot cycle
type: Concept
definition: sunspot cycle
related: Maunder minimum
related: butterfly diagram
related: solar activity
related: solar cycle
related: sunspot

sunspot group
type: Concept
definition: sunspot group
narrower: bipolar group
related: solar activity
related: sunspot number

sunspot number
type: Concept
alternative label: Wolf number
alternative label: relative sunspot number
definition: sunspot number
related: Maunder minimum
related: butterfly diagram
related: solar activity
related: solar cycle
related: sunspot group

sunspot
type: Concept
alternative label: sun spot
broader: starspot
change note: FVH: added ALT sun_spot, BT starspot (2007-OCT-8)
definition: sunspot
related: Evershed-effect
related: Wilson effect
related: active Sun
related: bipolar group
related: butterfly diagram
related: emerging flux
related: magnetic field
related: magnetic storm
related: penumbra
related: plage
related: prominence
related: solar activity
related: solar filament
related: sunspot cycle
related: umbra

Sunyaev-Zeldovich effect
type: Concept
alternative label: Sunyaev Zeldovich effect
definition: Sunyaev-Zeldovich effect
related: X-ray emission
related: background radiation
related: galaxy cluster
related: intracluster matter
related: microwave background

supercluster
type: Concept
definition: supercluster
related: galaxy cluster

superconducting tunnel junction
type: Concept
broader: detector
definition: super-conducting tunnel junction detector
history note: FVH: new (2007-SEP-21)
related: quantum mechanics

supergalactic coordinate system
type: Concept
broader: celestial coordinate system
definition: supergalactic coordinate system
history note: ES: new (2007-OCT-8)
related: galaxy cluster
related: supergalactic latitude
related: supergalactic longitude

supergalactic latitude
type: Concept
broader: latitude
definition: supergalactic latitude
history note: ES: (2007-OCT-8)
related: supergalactic coordinate system
related: supergalactic longitude

supergalactic longitude
type: Concept
broader: longitude
definition: supergalactic longitude
history note: ES: (2007-OCT-8)
related: supergalactic coordinate system
related: supergalactic latitude

supergiant
type: Concept
broader: high-luminosity star
broader: post-main sequence star
definition: supergiant star
narrower: A supergiant
narrower: B supergiant
narrower: F supergiant
narrower: G supergiant
narrower: K supergiant
narrower: O supergiant
narrower: early-type supergiant
narrower: late-type supergiant
related: Hubble Sandage variable star
related: Lc variable star
related: R Coronae Borealis star
related: hypergiant
related: irregular variable star
related: semi-regular variable star
related: supermassive star

supergranulation
type: Concept
broader: granulation
definition: supergranulation
related: solar surface

superhump
type: Concept
broader: variability
definition: superhump
related: SU Ursae Majoris star
related: accretion disk
related: precession

supermassive star
type: Concept
definition: supermassive star
related: massive star
related: supergiant

supernova envelope
type: Concept
definition: supernova envelope
related: shock wave
related: supernova

supernova remnant
type: Concept
alternative label: SNR
definition: supernova remnant
related: X-ray source
related: black hole
related: neutron star
related: pulsar
related: radio source
related: white dwarf
related: white hole

supernova
type: Concept
alternative label: SN
broader: high-luminosity star
broader: star
change note: FVH: moved presupernovas from UF to RT (2007-SEP-21)
definition: supernova
narrower: Type Ia supernova
narrower: Type Ib supernova
narrower: Type Ic supernova
narrower: Type II supernova
narrower: hypernova
related: Opik theory
related: cataclysmic variable star
related: e-process
related: frozen in element
related: gravitational collapse
related: mass-loss
related: neutrino
related: nova
related: nuclear fusion
related: nucleosynthesis
related: optical outburst
related: p process
related: pre-supernova
related: progenitor
related: pulsar
related: r-process
related: runaway star
related: s-process
related: shock
related: supernova envelope
related: support system

support system
type: Concept
definition: support system
related: instrument
related: supernova
related: telescope
scope note: combine with other terms

surface brightness
type: Concept
broader: brightness
definition: surface brightness
related: L galaxy
related: gravity darkening
related: photosphere
related: surface photometry
related: temperature
related: von Zeipel theorem

surface gravity
type: Concept
alternative label: acceleration of gravity
definition: surface gravity
related: diameter
related: gravitational force
related: gravity darkening
related: line width
related: luminosity
related: luminosity classification
related: mass

surface of celestial body
type: Concept
alternative label: surface celestial body
definition: surface [celestial body]
narrower: canyon
related: Moon
related: dust storm
related: geology
related: lunar dome
related: maria
related: petrology
related: photosphere
related: planet
related: satellite
related: topography
related: volatile
related: volcano
related: water ice

surface photometry
type: Concept
alternative label: area photometry
broader: photometry
definition: surface photometry
related: drift scan
related: galaxy
related: isophot
related: isophotal diameter
related: nebula
related: surface brightness

surface property
type: Concept
broader: property
definition: surface property
related: albedo
scope note: combine with other terms

survey
type: Concept
definition: survey
narrower: X-ray survey
narrower: sky survey
narrower: ultraviolet survey
related: atlas
related: catalog
related: radio source count
related: star distribution

SU Ursae Majoris star
type: Concept
broader: dwarf nova
definition: SU Ursae Majoris star
related: WZ Sagittae star
related: superhump

S Vulpeculae star
type: Concept
broader: long period variable star
broader: pulsating variable star
broader: semi-regular variable star
definition: S Vulpeculae star
related: Mira variable star
related: RV Tauri star

Swan band
type: Concept
broader: molecular band
definition: Swan band
related: carbon monoxide
related: molecular spectrum

SX Arietis star
type: Concept
alternative label: helium variable star
broader: cataclysmic variable star
broader: dwarf nova
broader: early-type variable star
broader: eruptive binary star
broader: magnetic variable star
change note: FVH: deleted wrong referernces to CV's (2007-OCT-2)
definition: SX Arietis star
related: alpha2 Canum Venaticorum star

SX Phoenicis star
type: Concept
broader: multi-periodic variable star
broader: population II star
broader: pulsating variable star
definition: SX Phoenicis star

symbiotic nova
type: Concept
broader: nova
broader: symbiotic star
definition: symbiotic nova

symbiotic star
type: Concept
broader: emission line star
broader: eruptive binary star
definition: symbiotic star
narrower: Z Andromedae star
narrower: symbiotic nova
related: P Cygni line profile
related: X-ray binary star
related: cataclysmic variable star
related: dust shell

symbol
type: Concept
definition: symbol
related: unit

synchronous detector
type: Concept
broader: detector
definition: synchronous detector

synchronous rotation
type: Concept
broader: rotation
definition: synchronous rotation
related: close binary star
related: orbit
related: rotating star

synchrotron radiation
type: Concept
broader: electromagnetic radiation
broader: radiation
definition: synchrotron radiation
narrower: cyclotron radiation
narrower: gyrosynchrotron radiation
related: Razin effect
related: bremsstrahlung
related: magnetohydrodynamics
related: non-thermal source
related: radiation mechanism
related: relativistic electron

synodic period
type: Concept
definition: synodic period
related: Solar System
related: conjunction
related: opposition
related: planet
related: syzygy

system
type: Concept
definition: system
narrower: absorption line system
scope note: combine with other terms

syzygy
type: Concept
definition: syzygy
related: conjunction
related: opposition
related: planet
related: synodic period
scope note: conjunction or opposition of planet

tail
type: Concept
definition: tail
related: comet
related: head tail galaxy
related: interacting galaxy
related: streamer

tangential velocity
type: Concept
broader: velocity
definition: tangential velocity
related: orbital velocity
related: radial velocity
related: rotational velocity

tantalum
type: Concept
alternative label: Ta
broader: fundamental chemical element
definition: tantalum (atomic number 73)
history note: FVH: new (2007-OCT-25)

t array
type: Concept
broader: array
broader: radio interferometer
definition: t array
related: y array

T association
type: Concept
alternative label: T-association
broader: star association
definition: T association
related: FU Orionis star
related: H alpha emission line star
related: Herbig-Haro object
related: RW Aurigae star
related: T Tauri star
related: flare star
related: flash star
related: irregular variable star
related: pre-main sequence star
related: young star
related: young star cluster

taxonomy
type: Concept
definition: taxonomy
related: classification

T dwarf
type: Concept
broader: brown dwarf
definition: T dwarf
history note: FVH: new (2007-OCT-2)
related: T subdwarf
related: low-mass star
related: spectral type

teaching in astronomy
type: Concept
alternative label: education
definition: teaching in astronomy

technetium line
type: Concept
broader: metal line
broader: spectral line
definition: technetium line
related: technetium

technetium star
type: Concept
definition: technetium star
related: N star
related: S star
related: technetium

technetium
type: Concept
alternative label: Tc
broader: fundamental chemical element
definition: technetium (atomic number 43)
history note: FVH: new (2007-OCT-25)
related: technetium line
related: technetium star

tektite
type: Concept
broader: meteorite
definition: tektite
narrower: australite
narrower: bediasite
narrower: indochinite
narrower: moldavite

telescope array
type: Concept
broader: array
definition: telescope array
related: filling factor
related: interferometer
related: telescope

telescope construction
type: Concept
definition: telescope construction
related: telescope

telescope design
type: Concept
definition: telescope design
related: telescope
related: telescope mounting

telescope instrument
type: Concept
alternative label: telescope instrumentation
broader: instrument
definition: telescope instrument
narrower: photometer
narrower: polarimeter
narrower: spectrograph
related: control system
related: detector
related: feed
related: feed horn
related: remote control system
related: spectrophotometer
related: telescope
scope note: not a complete list of terms

telescope mirror
type: Concept
broader: mirror
definition: telescope mirror
narrower: primary mirror
narrower: secondary mirror
narrower: tertiary mirror
related: telescope

telescope mounting
type: Concept
definition: telescope mounting
narrower: altazimuth mounting
narrower: equatorial mounting
related: coelostat
related: heliostat
related: polar axis
related: siderostat
related: telescope
related: telescope design

telescope
type: Concept
broader: optical instrument
definition: telescope
narrower: Cassegrain telescope
narrower: Gregorian telescope
narrower: automated telescope
narrower: gamma-ray telescope
narrower: grazing incidence telescope
narrower: infrared telescope
narrower: optical telescope
narrower: radio telescope
narrower: solar telescope
narrower: space telescope
related: antenna
related: control system
related: dome
related: drive
related: focus
related: guide system
related: observatory
related: optical aberration
related: pointing accuracy
related: pointing error
related: remote control system
related: support system
related: telescope array
related: telescope construction
related: telescope design
related: telescope instrument
related: telescope mirror
related: telescope mounting
related: vignetting
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

television camera
type: Concept
alternative label: TV camera
definition: television camera
related: television
related: television detector
related: two-dimensional detector

television detector
type: Concept
alternative label: TV camera
alternative label: television camera tube
broader: multi-channel detector
broader: photoelectronic device
broader: two-dimensional detector
definition: television detector
related: CCD detector
related: television
related: television camera

television
type: Concept
alternative label: TV
definition: television
related: television camera
related: television detector

telluric line
type: Concept
broader: spectral line
definition: telluric line
related: Earth atmosphere
related: spectral band
scope note: from Earth's atmosphere

tellurium
type: Concept
alternative label: Te
broader: fundamental chemical element
definition: tellurium (atomic number 52)
history note: FVH: new (2007-OCT-25)

temperature control
type: Concept
definition: temperature control
related: air conditioning
related: cryogenics
related: cryostat
related: dome
related: temperature distribution
related: ventilation

temperature distribution
type: Concept
definition: temperature distribution
related: temperature control
related: temperature zone

temperature effect
type: Concept
alternative label: thermal effect
definition: temperature effect
scope note: combine with other terms

temperature fluctuation
type: Concept
definition: temperature fluctuation
scope note: combine with other terms

temperature scale
type: Concept
definition: temperature scale
narrower: absolute temperature scale
narrower: celsius temperature scale
related: Kelvin

temperature
type: Concept
definition: temperature
narrower: brightness temperature
narrower: effective temperature
narrower: electron temperature
narrower: ion temperature
related: absolute temperature scale
related: celsius temperature scale
related: color
related: emissivity
related: limb brightening
related: limb darkening
related: radiative equilibrium
related: spectral type
related: surface brightness
related: thermal conductivity
related: thermodynamics
scope note: combine with other terms

temperature zone
type: Concept
definition: temperature zone
related: atmosphere
related: stellar interior
related: temperature distribution

terbium
type: Concept
alternative label: Tb
broader: fundamental chemical element
broader: rare earth
definition: terbium (atomic number 65)
history note: FVH: new (2007-OCT-25)

terminator line
type: Concept
definition: terminator line
related: lunar phase

terrestrial radiation
type: Concept
broader: atmospheric radiation
definition: terrestrial radiation
related: greenhouse effect
related: infrared radiation
scope note: ES: moved atmospheric_radiation from NT to BT (2007-OCT-8)

tertiary mirror
type: Concept
broader: telescope mirror
definition: tertiary mirror
history note: FVH: new (2007-SEP-21)
related: Nasmyth focus
related: optical telescope
related: primary mirror
related: reflecting telescope
related: secondary mirror
related: subreflector

tertiary star
type: Concept
broader: companion star
definition: tertiary star
history note: ES: new (2007-OCT-8)
related: primary star
related: secondary star

testing
type: Concept
definition: testing
scope note: combine with other terms

thallium
type: Concept
alternative label: Tl
broader: fundamental chemical element
definition: thallium (atomic number 81)
history note: FVH: new (2007-OCT-25)

theoretical astrophysics
type: Concept
broader: astrophysics
change note: FVH: moved ASTROPHYSICS to BT (2007-OCT-1)
definition: theoretical astrophysics

theory
type: Concept
definition: theory
related: research
scope note: combine with other terms

thermal conductivity
type: Concept
definition: thermal conductivity
related: conduction
related: temperature

thermal emission
type: Concept
broader: emission spectrum
definition: thermal emission
related: free-free emission
related: infrared emission

thermal equilibrium
type: Concept
definition: thermal equilibrium
related: Saha equation
related: local thermodynamic equilibrium
related: thermal instability
related: thermodynamic equilibrium
related: thermodynamics

thermal history
type: Concept
definition: thermal history
scope note: combine with other terms

thermal instability
type: Concept
definition: thermal instability
related: convection
related: local thermodynamic equilibrium
related: thermal equilibrium
related: thermodynamic equilibrium
related: turbulence Earth atmosphere
related: turbulence star atmosphere

thermal property
type: Concept
broader: property
definition: thermal property
scope note: combine with other terms

thermal radiation
type: Concept
broader: electromagnetic radiation
broader: radiation
definition: thermal radiation
related: Johnson noise
related: black body radiation
related: infrared radiation

thermal stability
type: Concept
definition: thermal stability
related: Rayleigh number
related: local thermodynamic equilibrium
related: thermodynamic equilibrium

thermal structure
type: Concept
definition: thermal structure
related: convection
related: turbulence Earth atmosphere
related: turbulence star atmosphere
scope note: combine with other terms

thermionic emission
type: Concept
alternative label: dark current
definition: thermionic emission
related: cathode
related: electron
related: ion

thermodynamic equilibrium
type: Concept
definition: thermodynamic equilibrium
narrower: local thermodynamic equilibrium
related: energy-transfer
related: thermal equilibrium
related: thermal instability
related: thermal stability
related: thermodynamics

thermodynamics
type: Concept
definition: thermodynamics
related: adiabatic process
related: energy-transfer
related: enthalpy
related: entropy
related: local thermodynamic equilibrium
related: plasma
related: temperature
related: thermal equilibrium
related: thermodynamic equilibrium

thermoluminescence
type: Concept
broader: luminescence
definition: thermoluminescence

thermonuclear reaction
type: Concept
definition: thermonuclear reaction
scope note: see nuclear fusion

thermosphere
type: Concept
definition: thermosphere
related: Earth atmosphere
related: exosphere
related: ionosphere
related: mesopause
related: upper atmosphere

thickness
type: Concept
definition: thickness
scope note: combine with other terms

thin film
type: Concept
broader: optical film
definition: thin film
narrower: aluminum coating
narrower: antireflection coating
narrower: silver coating
related: coating
related: mirror
related: optical surface
related: reflection
related: vacuum technique
related: vapor deposition

Thomson scattering
type: Concept
broader: Compton scattering
broader: light scattering
broader: radiation scattering
definition: Thomson scattering
related: Rayleigh scattering

thorium
type: Concept
alternative label: Th
broader: fundamental chemical element
definition: thorium (atomic number 90)
history note: FVH: new (2007-OCT-25)

three-body problem
type: Concept
alternative label: three body problem
definition: three-body problem
related: N-body problem
related: celestial mechanics
related: orbit
related: perturbation
related: stellar dynamics
related: two-body problem

three-dimensional spectroscopy
type: Concept
alternative label: three dimensional spectroscopy
broader: spectroscopy
definition: three-dimensional spectroscopy
related: three-dimensional spectrum

three-dimensional spectrum
type: Concept
alternative label: three dimensional spectrum
broader: spectrum
definition: three-dimensional spectrum
history note: FVH: new (2007-SEP-21)
related: extended object
related: integral field spectrograph
related: long slit spectrum
related: multi-fiber spectrograph
related: multi-slit spectrograph
related: spectrograph slit
related: three-dimensional spectroscopy
related: two-dimensional spectroscopy

thulium
type: Concept
alternative label: Tm
broader: fundamental chemical element
broader: rare earth
definition: thulium (atomic number 69)
history note: FVH: new (2007-OCT-25)

tidal disruption
type: Concept
definition: tidal disruption
related: Roche limit
related: differential rotation
related: star cluster
related: tidal distortion
related: tidal friction
related: tidal interaction
related: tidal radius

tidal distortion
type: Concept
definition: tidal distortion
related: differential rotation
related: interacting galaxy
related: tidal disruption
related: tidal friction
related: tidal interaction

tidal friction
type: Concept
definition: tidal friction
related: Earth-Moon system
related: close binary star
related: interacting binary star
related: interacting galaxy
related: tidal disruption
related: tidal distortion
related: tidal interaction
related: tide

tidal interaction
type: Concept
definition: tidal interaction
related: Roche lobe
related: interacting binary star
related: interacting galaxy
related: tidal disruption
related: tidal distortion
related: tidal friction

tidal radius
type: Concept
definition: tidal radius
related: star cluster
related: tidal disruption

tide
type: Concept
definition: tide
narrower: atmospheric tide
narrower: ocean tide
narrower: polar tide
related: tidal friction

time measurement
type: Concept
alternative label: time determination
definition: time measurement
related: time

time-resolved spectroscopy
type: Concept
broader: spectroscopy
definition: time-resolved spectroscopy
related: high-speed photometer
related: variable star

time signal
type: Concept
definition: time signal
related: global positioning system
related: time standard
related: time synchronization

time standard
type: Concept
definition: time standard
related: atomic clock
related: clock
related: global positioning system
related: time signal
related: time synchronization

time synchronization
type: Concept
alternative label: time synchronisation UK
definition: time synchronization
related: atomic clock
related: global positioning system
related: radio interferometry
related: time signal
related: time standard
related: very long baseline interferometry

time
type: Concept
definition: time
narrower: Universal Time
narrower: civil time
narrower: dynamical time
narrower: ephemeris time
narrower: mean solar time
narrower: sidereal time
related: Besselian epoch
related: Earth orbit
related: Earth rotation
related: Gregorian calendar
related: Julian Date
related: Julian epoch
related: astrometric instrument
related: atomic clock
related: calendar
related: chronometer
related: clock
related: ephemeris
related: epoch
related: general theory of relativity
related: time measurement
related: transit instrument
related: transit time
related: year

timing equipment
type: Concept
alternative label: timing device
definition: timing equipment
narrower: clock
narrower: pendulum

tin
type: Concept
alternative label: Sn
broader: fundamental chemical element
definition: tin (atomic number 50)
history note: FVH: new (2007-OCT-25)

tip-tilt mirror
type: Concept
alternative label: tip tilt mirror
definition: tip-tilt mirror
related: active optics
related: seeing
related: segmented optics

titanium oxide
type: Concept
alternative label: TiO
definition: TiO molecule
history note: FVH: new (2007-OCT-2)
related: L dwarf
related: M star
related: oxygen
related: titanium

titanium
type: Concept
alternative label: Ti
broader: fundamental chemical element
definition: titanium (atomic number 22)
history note: FVH: new (2007-OCT-25)
related: titanium oxide

topography
type: Concept
definition: topography
related: Earth
related: planet
related: satellite
related: surface of celestial body
scope note: combine with other terms

torus
type: Concept
definition: torus
related: circumstellar disk
related: interstellar matter

total eclipse
type: Concept
broader: eclipse
definition: total eclipse
related: annular eclipse
related: eclipsing binary star
related: partial eclipse
related: umbra

trace element
type: Concept
broader: chemical element
definition: trace element
related: metal abundance

tracking
type: Concept
definition: tracking
related: autoguider
related: control system
related: pointing accuracy
related: pointing error

trajectory
type: Concept
definition: trajectory
related: orbit

transfer function
type: Concept
definition: transfer function
narrower: modulation transfer function
narrower: optical transfer function
narrower: point spread function

transit circle
type: Concept
broader: transit instrument
definition: transit circle
related: transit telescope

transit instrument
type: Concept
broader: astrometric instrument
definition: transit instrument
narrower: meridian circle
narrower: transit circle
narrower: transit telescope
related: astrometry
related: meridian observation
related: time
related: transit

transition probability
type: Concept
definition: transition probability
related: g value
related: gf value
related: line formation
related: line width
related: oscillator strength
related: spectral line

transition region
type: Concept
definition: transition region
related: chromosphere
related: solar corona

transit telescope
type: Concept
broader: transit instrument
definition: transit telescope
narrower: zenith telescope
related: meridian observation
related: transit circle
related: transit time

transit time
type: Concept
definition: transit time
related: Right Ascension
related: hour angle
related: meridian observation
related: sidereal time
related: time
related: transit telescope

transit
type: Concept
definition: transit
related: astrometry
related: eclipse
related: occultation
related: transit instrument

transmission grating
type: Concept
broader: diffraction grating
definition: transmission grating
narrower: objective grating
related: VPH grating
related: echelle grating
related: grism
related: reflection grating

transmission
type: Concept
definition: transmission
related: absorption
related: optics
related: reflection
related: refraction
related: transparency
scope note: combine with other terms

trans-Neptunian object
type: Concept
alternative label: TNO
definition: trans-Neptunian object
history note: FVH: new (2007-OCT-2)
narrower: Edgeworth-Kuiper belt object
related: Edgeworth-Kuiper belt
related: Oort cloud
related: Solar System
related: asteroid

transparency
type: Concept
definition: transparency
related: absorption coefficient
related: atmospheric window
related: opacity
related: transmission

transplutonian planet
type: Concept
definition: transplutonian planet
related: Solar System

transport process
type: Concept
definition: transport process
related: radiative transfer

transverse velocity
type: Concept
broader: velocity
definition: transverse velocity
related: proper motion
related: radial velocity
related: space motion

trigonometric parallax
type: Concept
broader: parallax
definition: trigonometric parallax
related: Astronomical Unit
related: distance
related: nearby star

triple star
type: Concept
broader: multiple star
change note: FVH: moved MULTIPLE_STARS to BT (2007-OCT-1)
definition: triple star

tritium
type: Concept
broader: hydrogen
definition: tritium, an isotope of hydrogen
related: isotope

Trojan group
type: Concept
broader: minor planet family
definition: Trojan group
related: Amor group
related: Apollo group

tropical year
type: Concept
broader: year
definition: tropical year
related: Earth orbit

Tropic of Cancer
type: Concept
definition: Tropic of Cancer
related: Tropic of Capricorn
related: solstice
related: summer solstice

Tropic of Capricorn
type: Concept
definition: Tropic of Capricorn
related: Tropic of Cancer
related: solstice
related: winter solstice

tropopause
type: Concept
definition: tropopause
related: Earth atmosphere
related: stratosphere
related: troposphere

troposphere
type: Concept
definition: troposphere
related: Earth
related: Earth atmosphere
related: exosphere
related: tropopause

true anomaly
type: Concept
broader: orbital anomaly
change note: FVH: moved ANOMALY to BT (2007-OCT-1)
definition: true anomaly

true position
type: Concept
broader: position
definition: true position
related: apparent position
related: astrometry
related: coordinate system

T subdwarf
type: Concept
broader: brown dwarf
broader: subdwarf
definition: T subdwarf
history note: FVH: new (2007-OCT-9)
related: T dwarf

T Tauri star
type: Concept
alternative label: TTS
alternative label: YY Orionis star
broader: emission line star
broader: irregular variable star
broader: pre-main sequence star
change note: FVH: moved yy_orinois_star to ALT, added NT CLASSICAL_T_TAURI_STARS and WEAK_LINE_T_TAURI_STARS (2007-SEP-24)
definition: T Tauri star
narrower: FU Orionis star
narrower: classical T Tauri star
narrower: weak-line T Tauri star
related: Herbig-Haro object
related: RW Aurigae star
related: T association
related: emission nebula
related: protostar

Tully-Fisher relation
type: Concept
broader: statistical relation
definition: Tully-Fisher relation
related: cosmology
related: galaxy
related: line width
related: redshift

tungsten
type: Concept
alternative label: W
broader: fundamental chemical element
definition: tungsten (atomic number 74)
history note: FVH: new (2007-OCT-25)

turbidity
type: Concept
definition: turbidity
related: halation
related: photographic emulsion

turbulence Earth atmosphere
type: Concept
definition: turbulence [Earth atmosphere]
narrower: macroturbulence
narrower: microturbulence
related: Earth atmosphere
related: convection
related: point spread function
related: scintillation
related: seeing
related: thermal instability
related: thermal structure
scope note: in Earth's atmosphere

turbulence star atmosphere
type: Concept
definition: turbulence [star atmosphere]
narrower: macroturbulence
narrower: microturbulence
related: convection
related: line broadening
related: stellar atmosphere
related: thermal instability
related: thermal structure
scope note: in stellar atmosphere or in interstellar matter

turnoff point
type: Concept
definition: turnoff point
related: Hertzsprung-Russell diagram
related: age
related: giant branch
related: globular star cluster
related: main sequence
related: open star cluster

twilight
type: Concept
definition: twilight
related: Earth atmosphere
related: sky brightness
related: sunlight

two-body problem
type: Concept
alternative label: two body problem
definition: two-body problem
related: Earth-Moon system
related: N-body problem
related: binary star
related: celestial mechanics
related: planet
related: stellar dynamics
related: three-body problem

two-color diagram
type: Concept
alternative label: two color diagram
definition: two-color diagram
related: color index
related: photometry

two-color photometry
type: Concept
alternative label: two color photometry
broader: broad band photometry
definition: two-color photometry
narrower: BV photometry
related: Johnson photometry
related: Sloan photometry

two-dimensional detector
type: Concept
alternative label: two dimensional detector
broader: detector
definition: two-dimensional detector
narrower: CCD detector
narrower: image tube
narrower: television detector
related: charge-coupled device
related: charge-injection device
related: charge-transfer device
related: flat field
related: image processing
related: pixel
related: television camera

two-dimensional spectroscopy
type: Concept
alternative label: two dimensional spectroscopy
broader: spectroscopy
definition: two-dimensional spectroscopy
related: three-dimensional spectrum
related: two-dimensional spectrum

two-dimensional spectrum
type: Concept
alternative label: two dimensional spectrum
broader: spectrum
definition: two-dimensional spectrum
related: extended object
related: long slit spectrum
related: spectrograph slit
related: two-dimensional spectroscopy
scope note: FVH: added RT SPECTROGRAPH_SLITS (2007-SEP-21)

two-spectrum binary star
type: Concept
alternative label: spectrum binary star
alternative label: two spectrum binary star
broader: spectroscopic binary star
definition: two-spectrum binary star

Type Ia supernova
type: Concept
broader: supernova
definition: Type Ia supernova
history note: FVH: new (2007-OCT-1)
related: Type Ib supernova
related: Type Ic supernova
related: Type II supernova
related: cosmology

Type Ib supernova
type: Concept
broader: supernova
definition: Type Ib supernova
history note: FVH: new (2007-OCT-1)
related: Type Ia supernova
related: Type Ic supernova
related: Type II supernova

Type Ic supernova
type: Concept
broader: supernova
definition: Type Ic supernova
history note: FVH: new (2007-OCT-1)
related: Type Ia supernova
related: Type Ib supernova
related: Type II supernova

Type II supernova
type: Concept
broader: supernova
definition: Type II supernova
history note: FVH: new (2007-OCT-1)
related: Type Ia supernova
related: Type Ib supernova
related: Type Ic supernova

U Geminorum star
type: Concept
alternative label: SS Cygni star
broader: dwarf nova
change note: FVH: update (2007-SEP-24)
definition: U Geminorum star
related: UV Persei star
related: emission line star

ultraviolet astronomy
type: Concept
alternative label: UV astronomy
broader: space astronomy
definition: ultraviolet astronomy
related: balloon-borne instrument
related: rocket-borne instrument
related: satellite-borne instrument
related: space observatory
related: ultraviolet telescope

ultraviolet background
type: Concept
broader: background radiation
broader: ultraviolet radiation
definition: ultraviolet background
related: X-ray background
related: gamma-ray background
related: microwave background
related: radio background

ultraviolet camera
type: Concept
broader: camera
definition: ultraviolet camera

ultraviolet color
type: Concept
definition: ultraviolet color
related: ultraviolet photometry

ultraviolet continuum
type: Concept
broader: continuum radiation
broader: ultraviolet radiation
definition: ultraviolet continuum

ultraviolet detector
type: Concept
broader: detector
definition: ultraviolet detector
related: photometer

ultraviolet excess star
type: Concept
alternative label: UV excess star
definition: ultraviolet excess star
narrower: RW Aurigae star
related: metal-deficient star
related: metal-poor star

ultraviolet extinction
type: Concept
definition: ultraviolet extinction
related: atmospheric extinction
scope note: in Earth's atmosphere

ultraviolet filter
type: Concept
definition: ultraviolet filter
related: interference filter
related: optical filter

ultraviolet line
type: Concept
broader: spectral line
definition: ultraviolet line
related: line spectrum

ultraviolet luminosity
type: Concept
broader: luminosity
definition: ultraviolet luminosity

ultraviolet observatory
type: Concept
broader: observatory
definition: ultraviolet observatory
history note: FVH: new (2007-NOV-1)
narrower: Hubble Space Telescope
related: ultraviolet radiation

ultraviolet photography
type: Concept
broader: photography
definition: ultraviolet photography
related: camera

ultraviolet photometry
type: Concept
broader: broad band photometry
broader: medium band photometry
broader: photometry
definition: ultraviolet photometry
related: U magnitude
related: ultraviolet color
related: ultraviolet radiation

ultraviolet radiation
type: Concept
alternative label: ultraviolet_light
broader: electromagnetic radiation
broader: radiation
change note: FVH: change BT electromagnetic_wave to BT electromagnetic_radiation (2007-OCT-8)
definition: ultraviolet radiation
narrower: extreme ultraviolet radiation
narrower: far ultraviolet radiation
narrower: near ultraviolet radiation
narrower: ultraviolet background
narrower: ultraviolet continuum
related: Cerenkov radiation
related: Lyman continuum
related: Lyman series
related: black body radiation
related: line blanketing
related: ultraviolet observatory
related: ultraviolet photometry
related: ultraviolet spectrograph

ultraviolet source
type: Concept
alternative label: ultraviolet object
definition: ultraviolet source
narrower: early-type star

ultraviolet spectrograph
type: Concept
broader: spectrograph
definition: ultraviolet spectrograph
related: ultraviolet radiation

ultraviolet survey
type: Concept
broader: survey
definition: ultraviolet survey
related: catalog

ultraviolet telescope
type: Concept
broader: space telescope
definition: ultraviolet telescope
related: ultraviolet astronomy

ultraviolet
type: Concept
alternative label: UV
definition: ultraviolet
scope note: combine with other terms

U magnitude
type: Concept
broader: apparent magnitude
definition: U magnitude
related: Bessel photometry
related: Johnson photometry
related: ultraviolet photometry

umbra
type: Concept
definition: umbra
related: Wilson effect
related: eclipse
related: lunar eclipse
related: penumbra
related: solar eclipse
related: sunspot
related: total eclipse
related: zone of totality

underabundance
type: Concept
broader: abundance
definition: underabundance
history note: ES: new (2007-OCT-8)
related: overabundance

unit
type: Concept
definition: unit
related: metrology
related: symbol
scope note: of measurement

Universal Time
type: Concept
alternative label: U.T.
alternative label: UT
broader: time
definition: universal time
narrower: UT1
narrower: coordinated Universal Time
related: civil time
related: ephemeris time
related: mean solar time
related: solar day
related: year

universe
type: Concept
alternative label: cosmos
definition: universe
related: Dark Energy
related: cosmogony
related: cosmology
related: large scale structure
related: metagalaxy
scope note: see also under cosmology

unsharp masking
type: Concept
definition: unsharp masking
related: photographic processing
related: photography

upper atmosphere
type: Concept
definition: upper atmosphere
related: Earth atmosphere
related: aurora
related: exosphere
related: ionosphere
related: magnetosphere
related: mesosphere
related: thermosphere
related: van Allen radiation belt
scope note: Earth's atmosphere

upsilon Sagittarii star
type: Concept
broader: eclipsing binary star
definition: upsilon Sagittarii star

uranium
type: Concept
alternative label: U
broader: fundamental chemical element
definition: uranium (atomic number 92)
history note: FVH: new (2007-OCT-25)

Uranus
type: Concept
broader: Jovian planet
broader: planet
definition: Uranus
history note: FVH: new (2007-SEP-24)
related: Solar System

urca process
type: Concept
broader: nuclear reaction
definition: urca process

UT1
type: Concept
broader: Universal Time
definition: UT1
history note: FVH: new (2007-OCT-3)
related: coordinated Universal Time

UU Herculis star
type: Concept
broader: F supergiant
broader: irregular variable star
broader: post-asymptotic giant branch
change note: FVH: corrected content (2007-OCT-5)
definition: UU Herculis star

UV Ceti star
type: Concept
broader: flare star
broader: variable source
definition: UV Ceti star
related: flash star

UV Persei star
type: Concept
broader: cataclysmic variable star
definition: UV Persei star
related: U Geminorum star
related: dwarf nova

UX Ursae Majoris star
type: Concept
broader: nova-like variable
definition: UX Ursae Majoris-like star
related: AM Canum Venaticorum star
related: Z Camelopardalis star
related: dwarf nova

vacuum technique
type: Concept
definition: vacuum technique
related: aluminizing
related: aluminum coating
related: outgassing
related: thin film
related: vapor deposition

vacuum
type: Concept
definition: vacuum
related: pressure
related: space

vanadium
type: Concept
alternative label: V
broader: fundamental chemical element
definition: vanadium (atomic number 23)
history note: FVH: new (2007-OCT-25)

van Allen radiation belt
type: Concept
broader: radiation belt
definition: van Allen belt
definition: van Allen radiation belt
related: magnetohydrodynamics
related: upper atmosphere

vapor deposition
type: Concept
definition: vapor deposition
related: aluminum coating
related: coating
related: thin film
related: vacuum technique

variability
type: Concept
definition: variability
narrower: superhump
related: high-state
related: low-state
scope note: combine with other terms

variable source
type: Concept
broader: radio source
broader: source
definition: variable source
narrower: BL Lacertae object
narrower: UV Ceti star
narrower: active galactic nucleus
related: high-state
related: low-state
related: quasar

variable star
type: Concept
definition: variable star
narrower: cataclysmic variable star
narrower: eclipsing binary star
narrower: ellipsoidal variable star
narrower: intrinsic variable star
narrower: irregular variable star
narrower: peculiar variable star
narrower: pulsating variable star
narrower: semi-regular variable star
related: H alpha emission line star
related: He II ionization zone
related: OH IR star
related: Purkinje effect
related: amplitude
related: comparison star
related: fundamental frequency
related: high-speed photometer
related: light curve
related: maximum
related: minimum
related: period
related: period determination
related: phase shift
related: phase wave
related: time-resolved spectroscopy
related: velocity curve
related: visual observation
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

velocity curve
type: Concept
definition: velocity curve
related: light curve
related: maximum
related: minimum
related: period
related: phase shift
related: phase wave
related: spectroscopic binary star
related: variable star
related: velocity

velocity dispersion
type: Concept
definition: velocity dispersion
related: galaxy cluster
related: luminosity-dispersion relation
related: missing mass
related: star cluster
related: virial theorem

velocity distribution
type: Concept
definition: velocity distribution
related: galaxy cluster
related: star cluster
related: velocity
related: virial theorem

velocity ellipsoid
type: Concept
definition: velocity ellipsoid
related: velocity

velocity field
type: Concept
definition: velocity field
related: galaxy
related: shock wave
related: velocity
scope note: combine with other terms

velocity of light
type: Concept
alternative label: speed of light
broader: physical constant
broader: velocity
definition: velocity of light
related: apparent superluminal motion
related: ergosphere
related: event horizon
related: light cone
related: light year

velocity space
type: Concept
definition: velocity space
related: phase space
related: velocity

velocity
type: Concept
definition: velocity
narrower: angular velocity
narrower: escape velocity
narrower: heliocentric velocity
narrower: orbital velocity
narrower: parabolic velocity
narrower: peculiar velocity
narrower: radial velocity
narrower: relativistic velocity
narrower: rotational velocity
narrower: tangential velocity
narrower: transverse velocity
narrower: velocity of light
related: high-velocity cloud
related: high-velocity star
related: kinematics
related: momentum
related: velocity curve
related: velocity distribution
related: velocity ellipsoid
related: velocity field
related: velocity space
scope note: ES: added rotational_velocity (2007-OCT-11)
scope note: combine with other terms

ventilation
type: Concept
definition: ventilation
related: air conditioning
related: dome
related: dome seeing
related: temperature control
scope note: combine with other terms

Venus
type: Concept
broader: planet
definition: Venus
related: Solar System
related: ashen light

vernal equinox
type: Concept
broader: equinox
definition: vernal equinox
related: autumnal equinox

vertical circle
type: Concept
definition: vertical circle
related: altazimuth mounting
related: meridian circle

Very Large Array
type: Concept
alternative label: VLA
broader: very long baseline interferometer
definition: Very Large Array

very large telescope
type: Concept
broader: optical telescope
definition: very large telescope
related: multiple mirror telescope
related: segmented optics

very long baseline interferometer
type: Concept
alternative label: VLBI
broader: array
broader: interferometer
broader: radio interferometer
broader: radio telescope
definition: very long baseline interferometer
narrower: Very Large Array
related: long baseline interferometer

very long baseline interferometry
type: Concept
alternative label: VLBI
broader: interferometry
broader: radio interferometry
definition: very long baseline interferometry
related: atomic clock
related: long baseline interferometry
related: radio astrometry
related: time synchronization

vibrational spectrum
type: Concept
broader: spectrum
definition: vibrational spectrum
related: molecular spectrum
related: q branch

vibration
type: Concept
definition: vibration
related: amplitude
related: antinode
related: node
related: seismology
related: stability

vignetting
type: Concept
definition: vignetting
related: field of view
related: telescope
related: wide-field telescope

Vilnius photometry
type: Concept
broader: medium band photometry
definition: Vilnius photometry
related: Geneva photometry

virial theorem
type: Concept
definition: virial theorem
related: galaxy cluster
related: gravitation
related: radial velocity
related: star cluster
related: velocity dispersion
related: velocity distribution

virtual observatory
type: Concept
definition: virtual observatory
history note: FVH: new (2007-SEP-24)
related: data center
related: data retrieval
related: database

viscosity
type: Concept
definition: viscosity
related: plasma

visibility function
type: Concept
definition: visibility function
related: aperture synthesis
related: interference fringe
related: interferometry

visible radiation
type: Concept
alternative label: light
broader: electromagnetic radiation
change note: FVH: combined with light (2007-OCT-8)
definition: visible radiation
narrower: polarized light
related: color
related: darkness
related: gravitational lensing
related: light absorption
related: light interference
related: light scattering
related: luminescence
related: refraction
related: visible spectrum

visible spectrum
type: Concept
broader: spectrum
definition: visible spectrum
related: continuous spectrum
related: visible radiation

vision
type: Concept
definition: vision
narrower: color vision
related: dark adaption
related: image
related: visual acuity

visual acuity
type: Concept
definition: visual acuity
related: resolution
related: vision

visual binary star
type: Concept
broader: binary star
broader: wide binary star
definition: visual binary star
related: occulting disk
related: orbital motion
related: separation
related: visual observation
scope note: see also optical double star

visual magnitude
type: Concept
definition: visual magnitude
related: Purkinje effect
related: V magnitude
related: photovisual magnitude

visual observation
type: Concept
definition: visual observation
related: Purkinje effect
related: variable star
related: visual binary star

V magnitude
type: Concept
broader: apparent magnitude
definition: V magnitude
related: Bessel photometry
related: Johnson photometry
related: photovisual magnitude
related: visual magnitude

Voigt profile
type: Concept
definition: Voigt profile
related: absorption line
related: line spectrum

volatile
type: Concept
definition: volatile
related: planet
related: surface of celestial body

volcano
type: Concept
definition: volcano
related: crater
related: planet
related: satellite
related: surface of celestial body

von Zeipel theorem
type: Concept
definition: von Zeipel theorem
related: binary star
related: gravity
related: gravity darkening
related: rotating star
related: surface brightness

VPH grating
type: Concept
broader: diffraction grating
definition: VPH grating
history note: FVH: new (2007-SEP-21)
related: spectrograph
related: transmission grating

VY Sculpturis star
type: Concept
broader: nova-like variable
definition: VY Sculpturis star
related: Z Camelopardalis star

Walraven photometry
type: Concept
alternative label: VBLUW photometry
broader: medium band photometry
broader: photometric system
definition: Walraven photometry

water ice
type: Concept
alternative label: ice
definition: water ice
related: planet
related: surface of celestial body
related: water

water maser
type: Concept
broader: maser
definition: water maser
related: OH maser
related: SiO maser
related: water

water vapor
type: Concept
definition: water vapor
related: atmosphere
related: planet
related: water

water
type: Concept
broader: interstellar molecule
definition: water
related: water ice
related: water maser
related: water vapor

waveform analysis
type: Concept
definition: waveform analysis
related: Fourier analysis
related: period determination
related: spectroscopic analysis

waveguide
type: Concept
definition: waveguide
narrower: optical waveguide
narrower: radio waveguide

wavelength
type: Concept
definition: wavelength
related: acoustic wave
related: electromagnetic radiation
related: frequency
scope note: combine with other terms

wave motion
type: Concept
broader: motion
definition: wave motion
related: interference wave
related: spectroscopic analysis
related: wave propagation

wave propagation
type: Concept
definition: wave propagation
related: refraction
related: shock wave
related: wave
related: wave motion

wave
type: Concept
definition: wave
narrower: acoustic wave
narrower: drift wave
narrower: electromagnetic radiation
narrower: gravitational wave
narrower: gravity wave
related: oscillation
related: wave propagation

WCN star
type: Concept
broader: Wolf-Rayet star
change note: FVH: moved WOLF_RAYET_STARS to BT (2007-OCT-1)
definition: WCN star

WC star
type: Concept
broader: Wolf-Rayet star
change note: FVH: moved WOLF_RAYET_STARS to BT (2007-OCT-1)
definition: WC star

weak G band star
type: Concept
broader: giant
broader: metal-poor star
definition: weak G band star

weak gravitational lensing
type: Concept
broader: gravitational lensing
definition: weak gravitational lensing (resolved)
history note: FVH: new (2007-OCT-8)

weak interaction
type: Concept
broader: interaction
definition: weak interaction
narrower: Fermi interaction
related: nuclear physics
related: strong interaction
scope note: between atomic particles

weak-line T Tauri star
type: Concept
alternative label: WTTS
broader: T Tauri star
definition: weak-line T Tauri star
history note: FVH: new (2007-SEP-24)

weather station
type: Concept
broader: measuring instrument
definition: weather station
history note: FVH: new (2007-SEP-21)
related: altimeter
related: anemometer
related: barometer
related: wind vane

webcam
type: Concept
broader: camera
definition: webcam
history note: FVH: new (2007-SEP-21)

white dwarf
type: Concept
broader: compact object
broader: degenerate dwarf
broader: evolved star
broader: stellar object
change note: FVH: moved DA_star to NT, added DB_STARS (2007-OCT-1)
definition: white dwarf star
narrower: DA star
narrower: DB star
narrower: DO star
narrower: ZZ Ceti star
related: Chandrasekhar mass
related: X-ray pulsar
related: black dwarf
related: cataclysmic variable star
related: collapsed star
related: supernova remnant

white hole
type: Concept
definition: white hole
related: black hole
related: cosmology
related: gravitational lensing
related: naked singularity
related: supernova remnant

wide-angle lens
type: Concept
alternative label: wide angle lens
definition: wide-angle lens
related: all-sky camera
related: all-sky photography
related: camera

wide binary star
type: Concept
broader: binary star
change note: FVH: moved BINARY_STARS to BT and VISUAL_BINARY_STARS to NT (2007-OCT-1)
definition: wide binary star
narrower: visual binary star

wide-field telescope
type: Concept
alternative label: wide field telescope
broader: reflecting telescope
definition: wide-field telescope
narrower: Baker-Nunn camera
narrower: all-sky camera
related: Bouwers telescope
related: Maksutov telescope
related: Schmidt telescope
related: vignetting

Wilson-Bappu effect
type: Concept
alternative label: Wilson Bappu effect
definition: Wilson-Bappu effect
related: Ca II emission line
related: K line
related: absolute magnitude
related: late-type star

Wilson effect
type: Concept
definition: Wilson effect
related: penumbra
related: sunspot
related: umbra

window
type: Concept
definition: window
narrower: Galactic window
narrower: atmospheric window
related: interstellar absorption
scope note: combine with other terms

wind vane
type: Concept
broader: measuring instrument
definition: wind vane
history note: FVH: new (2007-SEP-21)
related: anemometer
related: weather station

winter solstice
type: Concept
broader: solstice
definition: winter solstice
related: Tropic of Capricorn
related: summer solstice

WN star
type: Concept
broader: Wolf-Rayet star
change note: FVH: moved WOLF_RAYET_STARS to BT (2007-OCT-1)
definition: WN star

Wolf diagram
type: Concept
definition: Wolf diagram
related: dark nebula
related: interstellar absorption

Wolf-Rayet star
type: Concept
broader: early-type emission star
definition: Wolf-Rayet star
narrower: WC star
narrower: WCN star
narrower: WN star
narrower: WR star
related: O star
related: carbon star
related: circumstellar envelope
related: ejecta
related: mass-loss

WR star
type: Concept
broader: Wolf-Rayet star
change note: FVH: moved WOLF_RAYET_STARS to BT (2007-OCT-1)
definition: WR star

W Ursae Majoris star
type: Concept
broader: detached binary star
broader: eclipsing binary star
definition: W Ursae Majoris star
related: Algol variable star

W Virginis star
type: Concept
broader: population II Cepheid
broader: pulsating variable star
definition: W Virginis star
narrower: BL Herculis star
related: Cepheid
related: RR Lyrae star

WZ Sagittae star
type: Concept
broader: dwarf nova
broader: long period variable star
definition: WZ Sagittae star
related: SU Ursae Majoris star

xenon
type: Concept
alternative label: Xe
broader: fundamental chemical element
definition: xenon (atomic number 54)
history note: FVH: new (2007-OCT-25)

X-ray absorption
type: Concept
broader: X-ray spectrum
definition: X-ray absorption
related: X-ray emission

X-ray astronomy
type: Concept
broader: space astronomy
definition: X-ray astronomy
related: X-ray spectrograph
related: X-ray telescope
related: balloon-borne instrument
related: rocket-borne instrument
related: satellite-borne instrument
related: space observatory

X-ray background
type: Concept
broader: background radiation
definition: X-ray background
related: X-ray radiation
related: gamma-ray background
related: microwave background
related: radio background
related: ultraviolet background

X-ray binary star
type: Concept
broader: X-ray source
broader: eruptive binary star
broader: interacting binary star
definition: X-ray binary star
narrower: cataclysmic variable star
narrower: high-mass X-ray binary star
narrower: low-mass X-ray binary star
related: HZ Herculis star
related: X-ray burst
related: X-ray nova
related: X-ray pulsar
related: X-ray star
related: black hole
related: dwarf nova
related: neutron star
related: symbiotic star

X-ray bright point
type: Concept
definition: X-ray bright point
related: close binary star
related: interacting binary star

X-ray burst
type: Concept
broader: burst
definition: X-ray burst
related: HZ Herculis star
related: X-ray binary star
related: X-ray transient
related: burster
related: gamma-ray burst
related: neutron star
related: optical burst
related: radio burst
related: rapid burst

X-ray continuum
type: Concept
broader: X-ray spectrum
broader: continuum radiation
definition: X-ray continuum

X-ray detector
type: Concept
broader: detector
definition: X-ray detector
related: proportional counter

X-ray diffraction
type: Concept
broader: diffraction
definition: X-ray diffraction
related: X-ray scattering
related: X-ray spectroscopy

X-ray emission
type: Concept
broader: X-ray spectrum
broader: emission spectrum
definition: X-ray emission
related: Sunyaev-Zeldovich effect
related: X-ray absorption

X-ray flare
type: Concept
broader: flare
definition: X-ray flare
related: active galaxy
related: active star

X-ray fluorescence
type: Concept
broader: fluorescence
broader: photoluminescence
definition: X-ray fluorescence

X-ray identification
type: Concept
definition: X-ray identification
related: X-ray source
related: optical identification

X-ray line
type: Concept
broader: emission line
definition: X-ray line
related: X-ray spectrum

X-ray luminosity
type: Concept
broader: luminosity
definition: X-ray luminosity
related: high-energy radiation

X-ray map
type: Concept
broader: map
definition: X-ray map
related: X-ray structure

X-ray nova
type: Concept
broader: nova
definition: X-ray nova
related: X-ray binary star

X-ray observatory
type: Concept
broader: observatory
broader: space observatory
definition: X-ray observatory

X-ray polarization
type: Concept
broader: light polarization
definition: X-ray polarization
related: polarized radiation

X-ray pulsar
type: Concept
broader: pulsar
definition: X-ray pulsar
narrower: HZ Herculis star
related: X-ray binary star
related: neutron star
related: white dwarf

X-ray quasar
type: Concept
broader: quasar
definition: X-ray quasar

X-ray radiation
type: Concept
alternative label: X-ray
broader: electromagnetic radiation
broader: high-energy radiation
broader: radiation
change note: FVH: moved X-ray to here (2007-OCT-8)
definition: X-ray radiation
related: X-ray background
related: X-ray scattering
related: X-ray source
related: X-ray spectrum

X-ray scattering
type: Concept
broader: radiation scattering
definition: X-ray scattering
related: Compton effect
related: X-ray diffraction
related: X-ray radiation

X-ray source
type: Concept
broader: source
definition: X-ray source
narrower: RS Canum Venaticorum star
narrower: X-ray binary star
narrower: active galactic nucleus
narrower: active galaxy
related: Seyfert galaxy
related: X-ray identification
related: X-ray radiation
related: X-ray star
related: eruptive binary star
related: optical identification
related: quasar
related: radio galaxy
related: relativistic star
related: supernova remnant

X-ray spectrograph
type: Concept
alternative label: X-ray spectrometer
broader: grazing incidence spectrograph
broader: spectrograph
definition: X-ray spectrograph
related: X-ray astronomy

X-ray spectroscopy
type: Concept
broader: spectroscopy
definition: X-ray spectroscopy
related: X-ray diffraction

X-ray spectrum
type: Concept
definition: X-ray spectrum
narrower: X-ray absorption
narrower: X-ray continuum
narrower: X-ray emission
related: X-ray line
related: X-ray radiation

X-ray star
type: Concept
broader: active star
broader: emission line star
definition: X-ray star
related: X-ray binary star
related: X-ray source
related: radio star

X-ray structure
type: Concept
definition: X-ray structure
related: X-ray map

X-ray survey
type: Concept
broader: survey
definition: X-ray survey

X-ray telescope
type: Concept
broader: grazing incidence telescope
broader: space telescope
definition: X-ray telescope
related: X-ray astronomy

X-ray transient
type: Concept
definition: X-ray transient
related: X-ray burst

Yagi antenna
type: Concept
broader: antenna
broader: directional antenna
broader: radio telescope
definition: Yagi antenna
related: half-wave dipole

y array
type: Concept
broader: array
broader: radio interferometer
definition: y-array
related: t array

year
type: Concept
definition: year
narrower: anomalistic year
narrower: cosmic year
narrower: tropical year
related: Universal Time
related: ephemeris time
related: light year
related: sidereal time
related: time

Yerkes classification
type: Concept
change note: FVH: removed NTs (2007-NOV-15)
definition: Yerkes galaxy classification scheme
history note: FVH: new (2007-OCT-12)
related: B galaxy
related: D galaxy
related: E galaxy
related: Ep galaxy
related: I galaxy
related: L galaxy
related: N galaxy
related: S galaxy
related: cD galaxy
related: galaxy

yoke mounting
type: Concept
broader: equatorial mounting
definition: yoke mounting

young disk Cepheid
type: Concept
broader: Cepheid
definition: young disc Cepheid UK
definition: young disk Cepheid

young star cluster
type: Concept
broader: open star cluster
definition: young star cluster
related: OB star
related: T association
related: population I star
related: young star

young star
type: Concept
broader: population I star
broader: star
definition: young star
narrower: B star
narrower: O star
narrower: OB star
narrower: blue straggler star
narrower: pre-main sequence star
related: H II region
related: OB association
related: R association
related: T association
related: young star cluster
scope note: only the broad classes are shown below; specific type will be found under these, or from the hierarchical list

ytterbium
type: Concept
alternative label: Yb
broader: fundamental chemical element
broader: rare earth
definition: ytterbium (atomic number 70)
history note: FVH: new (2007-OCT-25)

yttrium
type: Concept
alternative label: Y
broader: fundamental chemical element
broader: rare earth
definition: yttrium (atomic number 39)
history note: FVH: new (2007-OCT-25)

Z Andromedae star
type: Concept
broader: close binary star
broader: emission line star
broader: shell star
broader: symbiotic star
definition: Z Andromedae star

Z Camelopardalis star
type: Concept
broader: dwarf nova
definition: Z Camelopardalis star
related: UX Ursae Majoris star
related: VY Sculpturis star

Zeeman splitting
type: Concept
alternative label: line splitting
alternative label: spectral line splitting
broader: magneto-optical effect
definition: Zeeman splitting
related: Doppler broadening
related: Paschen-Back effect
related: Stark broadening
related: line broadening
related: line shift
related: natural line width
related: pressure broadening

zenith distance
type: Concept
definition: zenith distance
related: altitude angle
related: diurnal parallax
related: refraction angle

zenith hourly rate
type: Concept
definition: zenith hourly rate
related: meteor shower

zenith telescope
type: Concept
broader: refracting telescope
broader: transit telescope
change note: FVH: removed photographic_zenith_tube, moved zenith_tube to NT (2007-OCT-1)
definition: zenith telescope
narrower: zenith tube
related: meridian observation

zenith tube
type: Concept
alternative label: photographic zenith tube
broader: zenith telescope
definition: zenith tube

zenith
type: Concept
broader: pole
definition: zenith
related: celestial sphere
related: horizon coordinate system
related: nadir

zero-age horizontal branch
type: Concept
definition: zero-age horizontal branch
related: Hertzsprung-Russell diagram
related: giant branch
related: zero-age main sequence

zero-age main sequence
type: Concept
alternative label: ZAMS
definition: zero-age main sequence
related: Hertzsprung-Russell diagram
related: main sequence
related: zero-age horizontal branch

zero point
type: Concept
definition: zero point
scope note: combine with other terms

zinc
type: Concept
alternative label: Zn
broader: fundamental chemical element
definition: zinc (atomic number 30)
history note: FVH: new (2007-OCT-25)

zirconium star
type: Concept
definition: zirconium star
related: S star
related: giant
related: heavy metal star
related: molecular band
related: zirconium

zirconium
type: Concept
alternative label: Zr
broader: fundamental chemical element
definition: zirconium (atomic number 40)
history note: FVH: new (2007-OCT-25)
related: zirconium star

zodiacal dust cloud
type: Concept
definition: zodiacal dust cloud
scope note: see zodiacal dust

zodiacal dust
type: Concept
broader: dust
definition: zodiacal dust
related: gegenschein
related: interplanetary matter
related: meteoroid
related: meteoroid dust cloud
related: zodiacal light

zodiacal light
type: Concept
definition: zodiacal light
related: F corona
related: gegenschein
related: interplanetary matter
related: light scattering
related: night sky brightness
related: radiation scattering
related: sky brightness
related: zodiacal dust

zodiac
type: Concept
definition: zodiac
related: Earth orbit
related: astrology
related: constellation
related: ecliptic

zone of totality
type: Concept
definition: zone of totality
related: solar eclipse
related: umbra

ZZ Ceti star
type: Concept
broader: multi-periodic variable star
broader: pulsating variable star
broader: white dwarf
definition: ZZ Ceti star
related: He II ionization zone
related: kappa mechanism
related: non-radial pulsation