The diamond ring effect
A total Solar eclipse is one of the rarest and most beautiful astronomical events. For a few seconds, as bright light re-emerges from behind the Moon's obscuring disk, the Sun resembles a diamond ring, with the band of the ring formed by the faint glow from the hot gas in the Sun's corona - its ghostly, tenuous outer atmosphere.
Although the Sun and Moon appear almost exactly the same size from our perspective, the Sun is a much larger and much more distant body: about 150 million km from the Earth. Our first reliable measurement of this distance - which we call the astronomical unit - was provided by global observations of the 1769 Transit of Venus, an even rarer astronomical event whichalso occurred in June 2012, but won't be witnessed again until the year 2117.
Click here to find out about our Glasgow Science Festival event to celebrate the 2012 Transit of Venus, on June 5th/6th.
Image credit: David Cornfield, Massachussetts Institute of Technology