Jupiter

Jupiter is the 5th planet of the Sun and the largest in the Solar System. It is a gas giant with a mass exceeding two and a half times that of all the other planets in the Solar System together and slightly less than one-thousandth the mass of the Sun. Its diameter is 11 times that of Earth, and a tenth that of the Sun. Jupiter orbits the Sun at a distance of 5.20 Astronomical Units (778.5 Gm), with an orbital period of 11.86 Earth years. It is the third-brightest natural object in the Earth’s night sky, following the Moon and Venus, and has been observed since prehistoric times. Its name derives from that of Jupiter, the chief deity of ancient Roman religion.

Jupiter is the first of the Sun’s planets to form, and its inward migration during the primordial phase of the Solar System influenced much of the formation history of the other planets. Jupiter’s atmosphere consists of 76% hydrogen and 24 percent helium by mass, with a denser interior. It contains trace elements and compounds like carbon, oxygen, sulfur, neon, ammonia, water vapour, phosphine, hydrogen sulfide, and hydrocarbons. Jupiter’s helium abundance is 80% of the Sun’s , comparable to Saturn’s composition. The ongoing contraction of Jupiter’s interior generates more heat than the planet receives from the Sun. Its internal structure is believed to consist of an outer mantle of fluid metallic hydrogen and a diffuse inner core of denser material. Because of its rapid rate of rotation, one turn in 10 hours, Jupiter is an oblate spheroid; it has a small but noticeable bulge around the equator. The outer atmosphere is divided into a series of latitudinal bands, with turbulence and storms along their interacting boundaries; the most obvious result of this is the Great Red Spot, a giant storm recorded since 1831.

Jupiter’s magnetic field is the strongest and the second largest contiguous structure in the Solar System, generated by eddy currents within the fluid, metallic hydrogen core. The solar wind interacts with the magnetosphere, extending it outward and modifying Jupiter’s orbit. Jupiter is surrounded by a faint system of planetary rings that were found in 1979 by Voyager 1 and further examined by the Galileo orbiter in the 1990s. The Jovian ring system consists mainly of dust and has three major segments: an inner halo torus, a relatively bright main ring, and an outer gossamer ring. The rings have a reddish colour in the visible and near-infrared light. The age of the ring system is uncertain, perhaps dating back to Jupiter’s formation.

At least ninety-five moons orbit the planet; the four largest moons—Io, Europa, Ganymede, and Callisto—orbit within the magnetosphere, and were found by Galileo Galilei in the year 1610. Ganymede, the largest of the four, is larger than the planet Mercury. Since the year 1973, Jupiter has been visited by 9 robotic probes: seven flybys and 2 dedicated orbiters, and two additional en route.