Saturn

Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter.

 Description

Saturn is named after the Roman god Saturn, equated to the Greek Cronus (the Titan father of Zeus), the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol (♄) represents the Roman god's sickle. Saturn, along with Jupiter, Uranus and Neptune, is a gas giant. Together, these four planets are sometimes referred to as the Jovian planets, meaning "Jupiter-like". Saturn has an average radius about 9 times larger than the Earth's. While only 1/8 the average density of Earth, due to its larger volume, Saturn's mass is just over 95 times greater than Earth's. Because of Saturn's large mass and resulting gravitation, the conditions produced on Saturn are extreme if compared to Earth. The interior of Saturn is probably composed of a core of iron, nickel, silicon and oxygen compounds, surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium and finally, an outer gaseous layer. Electrical current within the metallic-hydrogen layer is thought to give rise to Saturn's planetary magnetic field, which is slightly weaker than Earth's and approximately one-twentieth the strength of Jupiter's. The outer atmosphere is generally bland in appearance, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h, significantly faster than those on Jupiter. Due to a combination of its lower density, rapid rotation and fluid state, Saturn is an oblate spheroid; that is, it is flattened at the poles and bulges at the equator. Its equatorial and polar radii differ by almost 10%—60,268 km versus 54,364 km.The other gas planets are also oblate, but to a lesser extent. Saturn is the only planet of the Solar System that is less dense than water (about 30% less). Although Saturn's core is considerably denser than water, the average specific density of the planet is 0.69 g/cm³ due to the gaseous atmosphere. Saturn is only 95 Earth masses,compared to Jupiter, which is 318 times the mass of the Earth, but only about 20% larger than Saturn.Saturn has a ring system that is divided into nine continuous and three discontinuous main rings (arcs), consisting mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-two known moons orbit the planet; fifty-three are officially named. This does not include the hundreds of "moonlets" within the rings. Titan, Saturn's largest and the Solar System's second largest moon (after Jupiter's Ganymede), is larger than the planet Mercury and is the only moon in the Solar System to possess a significant atmosphere. Saturn's atmosphere consists of 96.3% hydrogen and 3.25% helium, with traces of methane, ammonia, ethane, ethylene, and phosphine. Because Saturn is colder than Jupiter, the more colorful chemicals sink lower in its atmosphere and can't seen. The result is markings that are much less dramatic than those on Jupiter, although bands and some small spots are still visible. Alternate jet streams of east-west and west-east circulation, with speeds of up to about 1,800 km/h (1,100 mph), have been traced in the motion of the cloud tops and are responsible for the banded appearance of the planet. Electrical processes and heat from within Saturn enrich the layered chemical mixture of the atmosphere which probably transitions from superheated water near the core to ammonia ice at the observed cloud tops.