The Saturn, Discovering Our Solar System

• Discovered: Prehistoric times
• Diameter: 120,000 km
• Temperature: -130 °C (at cloud tops)
• Distance from the Sun: Varies between 1,351 and 1,510 million km
• Satellites: 52 officially named (and counting) including Titan

Named after the Roman god of agriculture, Saturn is the second largest planet in our Solar System. Its icy rocky core is surrounded by hydrogen and helium with traces of methane, ammonia and water ice.

Saturn, like Jupiter, is known as a gas giant. Engulfed in yellow clouds of ammonia, the planet’s wispy orange stripes result from 1,770 km per hour winds and hot air from the planet’s interior. It also spins rapidly on its axis, completing a full rotation every 10 hours 39 minutes.

The rings

Saturn is circled by a majestic halo of concentric rings and is the most distant planet visible to the naked eye. But Galileo Galilei, when he first viewed Saturn through a telescope in 1610, didn’t fully understand that he was also seeing a ring system. That honour went, a few years later, to the Dutch astronomer Christiaan Huygens, who had a better telescope.

It was two hundred years before astronomers realised that the rings weren’t solid but made from billions of pieces of ice and rock. These orbiting fragments range in size from a grain of sugar to a large house and are thought to be remnants from comets, asteroids and shattered moons.

The main rings are labelled A, B, C, D, and E but between 1979 - 81 Pioneer 11 and the Voyager space probes identified thousands more separate bands.

Moons

Saturn’s moons are numerous but not always easy to find among the rings. They have been discovered by Earth-based telescopes, the Voyager spacecraft and, most recently, the successful Cassini-Huygens mission. Cassini-Huygens is an ongoing collaboration between NASA, the European Space Agency (ESA) and the Italian Space Agency and involves UK scientists on both the Cassini orbiter and Huygens probe.

The astronomer Huygens discovered Titan, Saturn’s largest moon, which is bigger than both Mercury and Pluto. Since then a further 60 planetary satellites have been recorded, including Polydeuces, though not all have been officially named. Polydeuces was first detected by Professor Carl Murray of Queen Mary, University of London, and a member of the European Cassini-Huygens mission’s imaging team.

In January 2005, the Huygens probe descended by parachute through Titan’s atmosphere and survived for several hours on the surface. No one knew whether to expect a hard or soft landing. In fact it was somewhere in between. Later, in March 2007, the Cassini orbiter found evidence for seas in the northern parts of Titan that might be filled with liquid methane or ethane.

The Death Star

Another of Saturn's famous features is its moon Mimas, also known as the Death Star. The moon’s resemblance to the Death Star (the planet-destroying weapon in the film Star Wars) is due to its massive crater, 10 km deep and 130 km wide. It was caused by a collision with another body. For more information about Saturn, visit http://www.bnsc.gov.uk/content.aspx?nid=5946