Jupiter is the largest planet of the solar system. Its average distance to the sun is 5.2 AE. It circles round it every 11.9 years. Its equator diameter is 142'800 km, i.e. the 11fold of the earth, and its pole diameter amounts to 135'000 km. Its mass is 318 times the mass of the earth, and its density is 1,3 g / cm3. It is thus hardly denser than water. Because of its rapid rotation around its own axis it shows a strong flattening. Its small density lets assume that Jupiter consists mainly of light elements, like hydrogen and helium. Its force of gravity is 2,5 times bigger than here on earth, therefore not even the lightest gases can escape from its atmosphere. It is assumed that the composition of Jupiter is characteristic for the material, from which the earth and similar planets once developed. Its magnetic field is the strongest of the solar system. Also a radio and a synchrotron radiation coming from the planet were discovered, which are due to charged particles (electrons), that move inside its magnetic field. Due to the strong magnetic field and the weak solar wind, Jupiter has an enormous magnetosphaere. There is a rock core in the centre of the planet, with a mass possibly 10 to 20 times bigger than of the earth. The major part of the planet, into a depth of 25'000 km, consists of metallic hydrogen. In the1000 km thick layer above the hydrogen is liquid and very hot (several 1000°C). A 1000 km thick outside covering represents the atmosphere of the planet. It consists of hydrogen and helium, in the same relation as in the sun. Its structure consists of cloud layers, which can be bright ( zones formed by ascending gas flows) or dark (two " layers " parallel on both sides of the equator and formed by material sinking toward the inside of the planet). It contains oval marks and „garlands“ that keep changing all the time. On 22° south the "large red spot " appears, a hurricane of 40'000 x 14'000 km, rotating anti-clockwise. The margin of the " large red spot " is a high pressure area. The colour of the spot probably comes from phosphorus. Spots appear in stormy areas (with wind velocities up to 500 km/h). The movements of the spots are due to the mechanical influence of the wind. The existence of a ring was also proved. It is however too weak to be seen from the earth. It is divided into three layers, which consist of microscopic particles. The ring is 1.8 radii away from Jupiter and embedded into a halo (yard), which comprises the main ring of 30 km and the two smaller rings.
Oliver Flückiger
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