St.Louis Science Web


	Saturn is the sixth planet in order of distance from the Sun and the second largest in the Solar System. Saturn's most distinctive feature is its ring system, which was first seen in 1610 by Galileo, using one of the first telescopes. However, he did not realise that the rings were a


	separate body from the planet. He thought they were attached and therefore called them Saturn's 'handles'. The first astronomer to realise what they were was Christiaan Huygens, the Dutch astronomer. The planet lies at a distance of approximately 1.4 billion miles from the Sun and takes the equivalent of 29.5 Earth years to revolve once around the Sun. However it rotates at high speed, taking only 10.6 hours to complete one full rotation. The average temperature on Saturn is an extremely chilly -176 degrees centigrade. Its atmosphere consists mostly of Hydrogen and Helium but also contains traces of methane, ammonia, ethane, and phosphine. Unlike the planets of the Inner Solar System which have few or no satellites, Saturn has 20 moons including Mimas, Enceladus, Titan, Tethys, Dione and Cassini. The rings are 270,000 km in diameter, but only a few hundred meters thick. The particles from which they are made are generally only centimetres in size and are ice (some may be covered with ice); there are traces of silicate and carbon minerals. There are four main ring groups and three more faint, narrow ring groups separated by gaps called divisions. Recently, scientists have been able to study Saturn's rings at closer range thanks to images taken by the Hubble Space Telescope.