Saturn (/ˈsætɚn/ (help·info)) is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn, along with Jupiter, Uranus and Neptune, is classified as a gas giant. Together, these four planets are sometimes referred to as the Jovian planets, where Jovian is the adjectival form of Jupiter.
Saturn is named after the Roman god Saturnus, equated to the Greek Kronos (the Titan father of Zeus) and the Babylonian Ninurta. Saturn's symbol represents the god's sickle (Unicode: ♄).
The planet Saturn is composed of hydrogen, with small proportions of helium and trace elements. The interior consists of a small core of rock and ice, surrounded by a thick layer of metallic hydrogen and a gaseous outer layer. The outer atmosphere is generally bland in appearance, although long-lived features can appear. Wind speeds on Saturn can reach 1800 km/h, significantly faster than those on Jupiter. Saturn has a planetary magnetic field intermediate in strength between that of Earth and the more powerful field around Jupiter.
Saturn has a prominent system of rings, consisting mostly of ice particles with a smaller amount of rocky debris and dust. Sixty known moons orbit the planet. 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 km vs. 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. 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.
Though there is little 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 km a gaseous atmosphere. Traces of various ices are also present. The core region is estimated to be about 9–22 times the mass of the Earth. Saturn has a very hot interior, reaching 11 700 °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.
The outer atmosphere of Saturn consists of about 93.2% molecular hydrogen and 6.7% helium. Trace amounts of ammonia, acetylene, ethane, phosphine, and methane have also been detected. The upper clouds on Saturn are composed of ammonia crystals, while the lower level clouds appear to be composed of either ammonium hydrosulfide (NH4SH) or water. The atmosphere of Saturn is significantly deficient in helium relative to the abundance of the elements in the Sun.
The quantity of elements heavier than helium are not known precisely, but the proportions are assumed to match the primordial abundances from the formation of the Solar System. The total mass of these elements is estimated to be 19–31 times the mass of the Earth, with a significant fraction located in Saturn's core region.
Several small storms, smaller than the red eye of Jupiter form here.
- Saturday is named after Saturn
- Saturn is less dense than water, so it could possibly float.
- Saturn has a very high level of magnetism and sends out strong radio signals.
- Eary in 2009 as a space probe went through the atmosphere of Saturn, it picked up odd signals on the radio and heard very unusual sounds. Many people believed it was an alien signal. We have yet to figure out what is was, even though it is very likely that it was from the strong radio signals.
- Saturn's moon Encaladius, or Titan are possible places for life, many scientists believe.