Generalities: it is the giant planet of the Solar System. It is mainly constituted by hydrogen and helium. For this reason Jupiter has an essentially gaseous structure and therefore it doesn't show a real surface, as it happens for the rocky planets.
Going down into the depth of the planet  pressure becomes so high that  hydrogen is found for a notable thickness at the liquid state; when we approach  the center of the planet the pressure values  rise so that  hydrogen acquires the typical characteristics of  metals, and for this reason it is called metallic hydrogen .  Jupiter center is supposed to be formed by a rocky nucleus, approximatively as big as the Earth. Jupiter shows a very strong magnetic field, which is determined by the presence of  metallic hydrogen inside the planet.
Jupiter atmosphere  shows darker sides parallel to the equator and typical formations as the Great Red Cloud, owed to the complex meteorology of the planet. Jupiter atmosphere is in fact rather turbulent and it is characterized by notable tides of gaseous masses. The Red Cloud is a vortex of superior dimensions to those of the Earth. Its presence has been noticed since the beginnings of the telescopic era.
Surely the turbulence of Jupiter atmosphere is favoured by the fast rotation  of the planet on itself. Jupiter in fact  has the briefest day of the Solar System, since it employs less than 10 hours to complete a rotation. The rotation period  is not the same for every latitude: since it is not constituted by rigid material, Jupiter rotates in a more slightly  way than  the equator. The scarce rigidity of the material it is constituted by causes  its strong crushing to the poles. The centrifugal strength  in fact tends to expand it in correspondence to the equator.
Jupiter, like the other gaseous planets, has the characteristic to utter more energy than that  it receives  from the Sun; this means that it has an inside source of energy,  probably due to its slow contraction.

Observation: in the terrestrial sky Jupiter is an unmistakable object for brightness. It results in fact to be the brightest planet after Venus and for this reason it is the fourth star for brightness. Jupiter shines of not sparkling white-yellowish light and its brightness varies  of about one  magnitude (from -1.9 to -2.9) according to its distance from the Earth. The combined  motions of Earth and Jupiter take the giant planet to the opposite side every 13 months, but in reality  Jupiter’s observation  is possible and easy for many months every year. Because of its big dimensions, Jupiter is the planet that shows a disk of greater dimensions when it is observed by a  telescope.

Satellites: a small telescope is enough to observe Jupiter’s four biggest satellites . They were discovered by Galileo and for this reason they are called Galileian satellites. They are named, in order of distance from Jupiter, Io, Europa, Ganymede and Callisto. Io is of a bit superior dimensions to those of the Moon, and it is characterized by a notable volcanic activity. Europa is a bit smaller and it is covered with a layer of ice, under which an ocean of liquid water may be found. Ganymede is among the greatest satellites of the solar system (it is bigger than Mercury) and it has a frozen surface  rich in craters. Callisto is the second satellite for greatness, but it appears less bright because of its little reflecting surface.
The smallest satellites can’t be observed by amateur telescopes and some of them were discovered by  Voyager missions, being too small to be perceived from the Earth.
 
 

- Visibility of planets during this month

- Mutual position of Earth and external planets

Go back to Home Page