Jupiter is the largest planet in the Solar System and the fifth planet from the Sun. It is mostly composed of gas and, along with Saturn, Uranus and Neptune, is one of four gas giants in the Solar System.

When observed from Earth, Jupiter can appear as the third-brightest object in the night sky, after the Moon and Venus. Notable for its colourful wind-carved belts, this colossal planet is two-and-a-half times more massive than all the other planets combined, justifying the inspiration for its name, Jupiter, the king of the gods in Roman mythology. Compared to our Earth, its diameter is about 12 times larger.

Unlike the Earth, Jupiter is chiefly made up of hydrogen and helium gas that enters into a liquid state toward the planet’s centre. Deep inside this peculiar world is a solid rocky core about the size of Earth. The most prominent feature on Jupiter’s surface is the Great Red Spot, a huge storm that has raged for the past 300 years, covering an area about two times greater than the Earth. These features change and evolve with time: some spots appear and then vanish; whirlpools can be visible for a few years, before dissolving. Also, sometimes transient phenomena can be observed for a few weeks, such as the scars left by the fragments of Comet Shoemaker-Levy 9 in 1994, or very recently by a unknown asteroid or comet.

Astronomers have so far spotted over 60 moons orbiting Jupiter. The four largest moons — Ganymede, Io, Europa and Callisto — have been nicknamed the Galilean moons in honour of Galileo Galilei, the famous Italian astronomer who first observed them on 7 January 1610 through a homemade telescope. That discovery eventually revolutionised astronomy by challenging the old geocentric view of the world, as it was the first time an object was seen orbiting another planet.

The Pioneer and Voyager spacecraft passed close to Jupiter during their survey missions of the outer Solar System back in the 1970s, and the Galileo orbiter arrived at the planet in 1995. The most recent visit was paid by the New Horizons spacecraft during its flyby in 2007, when it used Jupiter’s gravity to accelerate on its way to Pluto.


ESO/S. Brunier

About the Image

Release date:3 December 2009, 23:21
Size:1575 x 1377 px

About the Object

Type:• Solar System : Planet : Type : Gas Giant

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