Saturn (symbol :) is the sixth planet from the sun and the second largest in the solar system, after Jupiter. It is named after the Roman god Saturn, and the astronomical symbol ♄ represents the god's sickle. Saturn is a gas giant with only ⅛ of the Earth's density, but with an average radius of nine times the Earth's, and with 95 times the Earth's mass. Saturn has the largest flattening (1/10) among the planets in the solar system.
Saturn probably has a core of iron, nickel and silicates, surrounded by a layer of metallic hydrogen, followed by layers of liquid hydrogen and helium, which eventually turn to gaseous form. The layer with metallic hydrogen conducts electric current, and is believed to give rise to the planet's magnetic field, which at the surface is somewhat weaker than the earth's, and approx. one-twentieth of Jupiter. The external atmosphere is mostly calm and without contrasts, but prolonged formations can occur. Wind speeds can reach 1,800 km / h - faster than on Jupiter, but not as fast as on Neptune. The large white spot is a known storm that takes place around the summer solstice every Saturn year in the northern hemisphere. One Saturn year corresponds to approx. 30 years on Earth. Saturn's ring system consists of nine continuous main rings and three discontinuous arcs, which consist mainly of ice particles, with also some rock and dust. 82 known moons orbit the planet - 53 of these have been given official names. In addition, there are hundreds of "dwarf moons" in the ring system. Titan, Saturn's largest and the solar system's second largest moon, is larger than the planet Mercury and is the only moon in the solar system with a significant atmosphere.
Saturn and Jupiter are classified as gas giants. Both planets consist mainly of the lightest elements; hydrogen and helium, which are found in liquid form in the interior of the planets, and which outwards towards the atmosphere gradually turn into gaseous form, which then gradually becomes thinner and thinner. None of the planets has any known solid (or liquid) surface, and for practical purposes the surface must therefore be defined. Elevations are normally stated in relation to the level in the atmosphere where the gas pressure has dropped to 0.1 bar. Saturn has the lowest density among the planets in the solar system. With an average density of 0.69 g / cm³, the planet is the only one in the solar system with a density lower than water; around 30% lower. The core is admittedly considerably denser, but the outer liquid and gas layers pull down the average. Saturn thus has "only" 95 times the mass of the earth, while it has 763 times the volume of the earth. In contrast, Jupiter has 318 times the mass of the earth, even though Jupiter is only approx. 20% larger than Saturn. Together, Jupiter and Saturn make up 92% of the planet's mass in the solar system. The low density also contributes to the planet being the most flattened in the solar system. Rotation means that none of the planets have the shape of perfect spheres, but as flat spheroids, slightly flattened at the poles and slightly bulging at the equator. For Saturn, the radii at the equator and at the poles deviate by almost 10% - 60,268 km and 54,364 km, respectively.
Inner structure and core
Saturn consists of about 96 volume percent hydrogen, which in 99.9% of the planet's mass is found in liquid form due to high pressure. Only in the outermost layer of the planet is hydrogen present as a gas, and there is no clear boundary between the two phases, because matter is above its critical point. The planet thus also has no well-defined surface. Inwards towards the core, temperature and pressure increase steadily, and eventually cause the hydrogen liquid to become metallic. In addition to hydrogen, there is around 3% by volume of helium and traces of various volatiles. Most physical models predict a solid core, but little is known about it. Models are based on the planet's mass, radius, period of rotation, flat pressure, gravitational moments, and state equations for the substances in the planet. Based on a review