Saturn

Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus the Titan father of Zeus the Babylonian Ninurta and to the Hindu Shani. Saturn's symbol represents the god's sickle Unicode .

Saturn, along with Jupiter, Uranus and Neptune, is classified as a gas giant. Together, these four planets are sometimes referred to as the Jovian, meaning "Jupiter-like", planets. Saturn has an average radius about nine-times larger than Earth's. 12 While only one-eighth the average density of Earth, due to its larger volume, Saturn's mass is just over ninety-five times greater than Earth's.

Because of Saturn's large mass and resulting gravitation, the conditions produced on Saturn are extreme. The interior pressures and temperatures are beyond what can be reproduced experimentally on Earth. The interior of Saturn is likely 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 an outer gaseous layer. 14 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 magnetic field and approximately one-twentieth the strength of the field around Jupiter. 15 The outer atmosphere is generally bland in appearance, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 160 km h, significantly faster than those on Jupiter.

Saturn has nine rings, consisting mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-two 16 known moons orbit the planet, fifty-three are officially named. This is not counting 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.

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 60,268 160 km versus 54,364 160 km. 5 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. Although Saturn's core is considerably denser than water, the average specific density of the planet is 0.69 160 g cm due to the gaseous atmosphere. Saturn is only 95 Earth masses, 5 compared to Jupiter, which is 318 160 times the mass of the Earth 18 but only about 20 larger than Saturn.

Though there is no direct information about Saturn's internal structure, it is thought that its interior is similar to that of Jupiter, having a small rocky core surrounded mostly by hydrogen and helium. The rocky core is similar in composition to the Earth, but denser. Above this, there is a thicker liquid metallic hydrogen layer, followed by a layer of liquid hydrogen and helium, and in the outermost 1000 160 km a gaseous atmosphere. 20 Traces of various volatiles are also present. The core region is estimated to be about 9 22 160 times the mass of the Earth. 21 Saturn has a very hot interior, reaching 11,700 160 C at the core, and it radiates 2.5 times more energy into space than it receives from the Sun. Most of the extra energy is generated by the Kelvin-Helmholtz mechanism slow gravitational compression , but this alone may not be sufficient to explain Saturn's heat production. An additional proposed mechanism by which Saturn may generate some of its heat is the "raining out" of droplets of helium deep in Saturn's interior, the droplets of helium releasing heat by friction as they fall down through the lighter hydrogen.