The sixth planet in outward succession from the Sun, Saturn takes its name from Saturnus, the Roman god of agriculture and the original ruler of the ancient gods. Saturn was the fifth and outermost of the planets know in antiquity.
From Earth, Saturn appears to the unaided eye as a yellowish object, brighter than most stars. A moderate telescope reveals its spectacular system of rings. First observed by Galileo in 1610, the rings were not recognized as such until the Dutch astronomer Christiaan Huygesn investigated them in the 1650s. Since then they have continued to fascinate observers.
Until the 1970s Saturn was thought to be the only planet with rings, but modern investigations by spacecraft have shown that both Jupiter and Uranus have them too, although in neither case can they compare with the splendor of the rings of Saturn. When seen edge-on the rings almost disappear from view. They are at their best when in "open" position.
Saturn is the second largest planet in the Solar System after Jupiter. It is over 95 times as massive as the Earth, and its volume exceeds that of the Earth by more than 740 times. Saturn is markedly flattened at the poles. These makes its diameter as measured at the equator about 12 per cent larger than it is as measured at the poles. The equatorial diameter is 120,660 kilometers (74,975 miles), nearly 9½ times that of the Earth. It takes about 29 years to complete one circuit of the Sun orbiting it at a distance of 1 billion 472 million kilometers (914 million miles).
The Rings of Saturn
Saturn has seven separate flat rings that girdle the planet in the plane of its equator. The rings consist of countless particles of all size ranging from dust grains and tiny pieces of water ice right up to boulders of the same dimensions as small asteroids. These larger particles, "moonlets" orbiting Saturn, are less numerous than the dust and ice grains, and use their gravitational influence to keep the smaller particles together and stop the rings from breaking up. Because of this, these moonlets are often called "shepherds".
The Moons of Saturn
At least 21 satellites orbit Saturn. The smallest are 80 kilometers (50 miles) or less in diameter. By far the largest is Titan, who is some 5,100 kilometers (3,170 miles), in diameter. Titan is larger than the planet Mercury and is the only satellite in the Solar System that has an atmosphere. Titan circles Saturn once every 16 days at an average distance of 1,200,000 kilometers (745,800 miles) from the planet's center. All the other satellites of Saturn are ice-covered bodies, many of which are marked by impact by crates. Phoebe, the outer-most satellite, travels in the opposite direction to the others. It is probably a captured asteroid.
Facts about Saturn Average Distance from the Sun: 1 billion 472 million kilometers (914 miles)
Length of Saturnian year: 29.46 Earth years
Length of Saturnian day: 10 hours 39.4 minutes
Equatorial Diameter: 120,660 kilometers (74,975 miles)
Polar diameter: 108,000 kilometers (67,110 miles)
Mass: 95.26 (Earth=1)
Density: 0.7 (water=1; Saturn will float on water)
Average Temperature of Outer Atmosphere: -180°C (-292°F)
Satellites: At least 21.
© 1988 Encyclopaedia Britannica, Inc.