|the brightness of a star in comparison with that of the sun: the luminosity of Sirius is expressed as 23 and indicates intrinsic brightness 23 times greater than the sun|
|a large system of stars held together by mutual gravitation and isolated from similar systems by vast regions of space|
|1.||See also Titan one of the giant planets, the sixth planet from the sun, around which revolve planar concentric rings (Saturn's rings) consisting of small frozen particles. The planet has at least 30 satellites. Mean distance from sun: 1425 million km; period of revolution around sun: 29.41 years; period of axial rotation: 10.23 hours; equatorial diameter and mass: 9.26 and 95.3 times that of the earth, respectively|
|2.||a large US rocket used for launching various objects, such as a spaceprobe or an Apollo spacecraft, into space|
|3.||the alchemical name for lead|
|Saturn (sāt'ərn) Pronunciation Key
The sixth planet from the Sun and the second largest, with a diameter about ten times that of Earth. Saturn is a gas giant that is almost as large as Jupiter in diameter but with only about 30 percent of Jupiter's mass. Its mainly gaseous composition together with its rapid axial rotation (it rotates once every 10.5 hours) cause a noticeable flattening at the poles and a prominent equatorial bulge. Saturn is encircled by a large, flat system of rings made up of rock fragments and tiny ice crystals, first observed by Galileo in 1610. The rings are believed to be unstable and therefore likely of recent origin; they may have been formed from bodies such as asteroids or moons that were shattered as they approached closer than the Roche limit. Saturn has numerous moons, of which the largest is Titan, the second largest moon in the solar system after Jupiter's Ganymede and larger than both Mercury and Pluto. See Table at solar system.
The Roman name for one of the Titans, the father of Zeus. In Roman mythology, Saturn fled from Mount Olympus after Zeus defeated the Titans. He settled in Italy and established a golden age, in which all people were equal and harvests were plentiful.
Note: Saturday (“Saturn's day”) is named after Saturn.
In astronomy, the second-largest major planet, sixth from the sun. Saturn was named for the Roman god of agriculture. Like Jupiter, Saturn is composed largely of gases and liquids. Saturn is the most distant planet plainly visible to the naked eye. (See solar system; see under “Mythology and Folklore.”)
Note: Saturn, often called the most beautiful planet, is known for the rings that encircle it.