The sixth planet from the Sun, notable for its ring system - first seen by Galileo in 1610, and first explained by Christiaan Huygens in 1656. It has 18 known moons, the largest of which, Titan, has an atmosphere. Its main characteristics are: mass 5.69 × 1026 kg; mean density 0.69 g / cm3; equatorial radius 60 000 km / 37 000 mi; polar radius 53 500 km / 33 300 mi; rotational period (equatorial) 10 h 14 m; orbital period 29.5 years; inclination of equator 27°; mean distance from the Sun 9.54 AU (887 million miles).
Saturn is a very large gas planet which spins very rapidly on its axis. It spins so fast that it flattens out the top and the bottom of the planet and bulges at its equator. Saturn's atmosphere has winds which can blow at over 1800 kilometers per hour! The white spots on Saturn are believed to be powerful storms.
Rings
The Ringed Planet, Saturn is probably the most visually stunning planet in our solar system. Saturn is surrounded by over 1000 rings made of ice and dust. These rings are actually made of of thousands of small particles of dust and ice. The size of the particles in the rings range from pebble-size to house-size. Scientists believe that the particles came from the destruction of moons circling the planet. As comets and meteorites smashed the moons, Saturn's gravitational pull shaped the particles into rings.
The divisions in the rings we see from Earth are caused by some of Saturn's smaller moons. Saturn has at least 18 known moons. Some of these moons orbit the planet within the rings, creating gaps in the rings.
The two outermost rings are separated by a dark band called the Cassini Division, named for the astronomer who discovered it in 1675. The Cassini division isn't empty, but it has less material in it. The middle ring is the brightest, and just inside it is a fuzzy one that can be difficult to spot.
The rings were observed by Voyager to have particle-size distribution ranging up to several metres. Their infrared signature suggests that they are made of water ice - possibly created by break-up of a moon whose orbit decayed inside the limit where tidal flexing exceeded the moon's material strength.
The rings show a complex structure including several divisions and innumerable 'ringlets'.
Moons
The moons, except Titan, are low in density, indicating that they are mainly composed of ices, but still with some 'rocky' material which comprises the core. All appear to be locked in synchronous orbits about Saturn. They have all been subject to meteoritic bombardment, and exhibit cratered surfaces.
Composition
Like Jupiter, it is a hydrogen / helium planet with a presumed innermost core of rocky composition and several Earth masses, an outer core of metallic hydrogen and helium, a liquid mantle of hydrogen / helium, and an atmosphere about 1000 km / 600 mi deep.
Also, like Jupiter, it is believed to have several cloud layers: solid ammonia (the highest), ammonium hydrosulphide, water ice, and water-ammonia. It is less colourful than Jupiter, and less vividly banded, possibly due to greater obscuration by ammonia clouds. It has less obvious discrete features such as vortices, but Voyager images do reveal definite structure within the bands of clouds.
Saturn is the sixth planet from the Sun. It is a gas giant, the second-largest planet in the solar system after Jupiter. It was named after the Roman god Saturn.
