Saturn is named after the Roman god of agriculture Saturn, the father of Jupiter, the king of the Roman gods. Saturnalia is an Ancient Roman festival that was held in honor of the god Saturn. Saturn is bright enough to be seen without a telescope. It will be visible near the constellation Virgo and star Spica in the early morning in January 2011. It will be visible in the same constellations all year, but will rise earlier each month.
Saturn’s most interesting feature is its rings. They appear to be ‘handles’ sticking out of the planet in a small telescope, and Galileo was puzzled by them. Huygens, who had a more powerful telescope than Galileo’s, saw that Saturn was surrounded by a flat ring. Cassini discovered a division between the A and B rings, the first of many subdivisions of the rings. The rings also have visible spokes, which are still not totally understood. In 2009, the rings were edge on when seen from Earth and were hardly visible. Saturn’s rings are made of billions of ice particles, and are guided in their orbits by shepherd moons.
Saturn has many moons. There are 7 major moons, but there are currently 53 named moons and others yet to be named. Saturn’s largest moon, Titan, is the only moon in the solar system to possess an atmosphere, which is approximately 95 percent nitrogen with traces of methane. The shepherd moons are Pan, Daphnis, Atlas, Prometheus and Pandora . The moons Janus and Epimetheus have similar orbits, they would collide if they attempted to pass each other. But instead of colliding, they swap orbits every four years.
Saturn is a gas giant, the second largest planet after Jupiter. Saturn is the only planet in our solar system that is less dense than water, it is only 70 percent as dense as water. It is composed 88 percent hydrogen and 11 percent helium, with traces of methane, ammonia and other elements. The upper clouds on Saturn are composed of ammonia crystals and lower clouds are composed of water. The hydrogen is compressed into metallic hydrogen near the core. Electric currents in this metallic hydrogen generate Saturn’s magnetic fields. In comparison, Earth is 5.5 times as dense as water, and is made of rock with an iron core.
Saturn emits two and a half times as much heat as it receives from the sun. The cloud tops of the planet’s thick atmosphere are quite cold, at –178°C. But the interior of the planet is very hot, reaching 11,700 °C , due to energy being generated by gravitational compression and sinking helium.
Saturn bulges at the equator, due to the fast rotation on its axis. A day on Saturn is equal to 10 hours and 40 minutes. This rapid spinning causes Saturn to bulge at its equator, the planet is 8,000 miles wider at its equator (74,000 miles) than the distance between the poles (66,000 miles).
A year on Saturn is equal to 29.5 Earth years. The planet’s axis and the rings remain at the same tilt as Saturn orbits the sun. So about every 15 years, the rings appear edge on to Earth.
Saturn is the sixth planet from the sun, at 887,000,000 miles it is nearly twice as far away from the Sun as Jupiter is.
Saturn has been visited by four space missions. There were flybys by NASA’s Pioneer 11 and by the Voyager 1 and 2 spacecraft. The Cassini spacecraft arrived at Saturn in July 2004 and went into orbit around the planet. The Huygens probe was detached from Cassini to explore Titan.
Saturn has played a part in several books and movies. It is mentioned in Micromégas (1752) by Voltaire and Off on a Comet (1877) by Jules Verne. It was also in the films Silent Running (1972) and Beetlejuice (1988). But the Pandora in Avatar (2009) was a moon of the gas giant Polyphemus in the fictional Alpha Centauri A system, not Saturn’s moon Pandora or even Titan.