Saturn is the sixth planet fromthe Sun and the second-largest in the Solar System, after Jupiter. Itis a gas giant with an average radius of about nine and a half timesthat of Earth. It has only one-eighth the average density of Earth;however, with its larger volume, Saturn is over 95 times moremassive.
Saturn's interior is most likelycomposed of a core of iron–nickel and rock (silicon and oxygencompounds). Its core is surrounded by a deep layer of metallichydrogen, an intermediate layer of liquid hydrogen and liquid helium,and finally, a gaseous outer layer. Saturn has a pale yellow hue dueto ammonia crystals in its upper atmosphere. An electrical currentwithin the metallic hydrogen layer is thought to give rise toSaturn's planetary magnetic field, which is weaker than Earth's, butwhich has a magnetic moment 580 times that of Earth due to Saturn'slarger size. Saturn's magnetic field strength is around one-twentiethof Jupiter's. The outer atmosphere is generally bland and lacking incontrast, although long-lived features can appear. Wind speeds onSaturn can reach 1,800 km/h (1,100 mph; 500 m/s), higher than onJupiter but not as high as on Neptune.
The planet's most notable feature isits prominent ring system, which is composed mainly of ice particles,with a smaller amount of rocky debris and dust. At least 83 moons areknown to orbit Saturn, of which 53 are officially named; this doesnot include the hundreds of moon-lets in its rings. Titan, Saturn'slargest moon and the second largest in the Solar System, is largerthan the planet Mercury, although less massive, and is the only moonin the Solar System to have a substantial atmosphere.
Name and symbol
The symbol for Saturn in late Classical(4th & 5th c.) and medieval Byzantine (11th c.) manuscripts,derives from ⟨κρ⟩ (kappa-rho).
Saturn is named after the Roman god ofwealth and agriculture and father of Jupiter. Its astronomical symbol(♄) has been traced back to the Greek Oxyrhynchus Papyri, where itcan be seen to be a Greek kappa-rho with a horizontal stroke, as anabbreviation for Κρονος (Cronus), the Greek name for theplanet. It later came to look like a lower-case Greek eta, with thecross added at the top in the 16th century to Christianize this pagansymbol.
The Romans named the seventh day of theweek Saturday, Sāturni diēs ("Saturn's Day"), for theplanet Saturn.
Physical characteristics
Saturn is a gas giant composedpredominantly of hydrogen and helium. It lacks a definite surface,though it is likely to have a solid core. Saturn's rotation causes itto have the shape of an oblate spheroid; that is, it is flattened atthe poles and bulges at its equator. Its equatorial and polar radiidiffer by almost 10%: 60,268 km versus 54,364 km. Jupiter, Uranus,and Neptune, the other giant planets in the Solar System, are alsooblate but to a lesser extent. The combination of the bulge androtation rate means that the effective surface gravity along theequator, 8.96 m/s2, is 74% of what it is at the poles and is lowerthan the surface gravity of Earth. However, the equatorial escapevelocity of nearly 36 km/s is much higher than that of Earth.
Saturn is the only planet of the SolarSystem that is less dense than water—about 30% less. AlthoughSaturn's core is considerably denser than water, the average specificdensity of the planet is 0.69 g/cm3 due to the atmosphere. Jupiterhas 318 times Earth's mass, and Saturn is 95 times Earth's mass.Together, Jupiter and Saturn hold 92% of the total planetary mass inthe Solar System.
