Saturn's rings
Saturn is famous as the 'lord of the rings', even though the other three giant gas planets – Jupiter, Uranus and Neptune – also have rings. Saturn's system takes pride of place, since its rings are extremely bright and very large.
They may be the remains of a satellite or a comet that broke apart. When they were discovered in the 17th century, drawings showed them looking like huge 'Mickey Mouse ears' on either side of the planet. As telescopes improved, astronomers realised that they are made of millions of fragments of ice and rock. Gaps in the rings have been cleared by the gravity of nearby moons.
Like a giant compact disk, the flat rings are more than 275 000 km across – wide enough to fill most of the gap between the Earth and Moon – but less than 1 km thick. As Saturn and Earth move up and down in their orbits, our view of the rings changes. In 2003, they were at their brightest and best. But every 15 years we see them edge on. They are then invisible in all but the largest telescopes. This is a good time to look for small moons near the rings.
Last modified 02 December 2004
