Jupiter is the fifth planet from the sun. Jupiter is the largest planet in the solar system, and is one of the brightest objects in the night sky. Jupiter is about 780 million km (484 million miles) from the sun, rotating around the sun once every 11.9 (Earth) years. Jupiter completely rotates on its axis once every 9.9 hours.

Jupiter is made up of gas. the core, made of iron and molten rock, is comparatively small. Jupiter has the shape similar to a squashed sphere - the diameter of Jupiter at the equator is 143,000 km (89,000 mi) though the diameter through Jupiter's rotational axis is over 10,000 km (6,000 mi) less.

Jupiter has a very strong magnetic field, approximately ten times stronger than that of Earth. Jupiter mostly consists of light elements such as helium and hydrogen, and is known to have strong winds. It is believed that Jupiter's core is made up of rock and metal, about the same density of Earth's core.

Jupiter's outer layer cosists of helium, hydrogen and other gases. this outer layer is estimated to be 1,000 km (600 mi) thick. Beneath these gases, the conditions are very hot and the pressure is very high. The core, consisting of rock and metal, has a radius of around 10,000 km.

The Great Red Spot is Jupiter's most famous storm, and has been active for centuries. The cause of the Great red Spot has not been discovered. It is suggested that the colour of the spot is caused by impurities.

The Shoemaker-Levy 9 comet hit jupiter in 1994. The comet was split into fragments as it approached, with the fragments striking Jupiter with speeds of up to 216,000 km/h (134,000 mph).

Moons

Jupiter is known to be orbited by 16 satellites and several thin rings of debris. The rings of debris appear to be orbiting progressively closer to Jupiter, suggesting that they will eventually collide with the planet.

Metis orbits Jupiter at a distance of 127,960 km (79,510 mi). Adrastea revolves around Jupiter at a distance of 128,980 km (80,140 mi). Amalthea is 135 km (84 mi) across and circles Jupiter at a distance of 181,300 km (112,700 mi). Thebe orbits Jupiter at a distance of 221,900 km (137,900 mi).

The Galilean moons, so called because their discoverer was Galileo, are four satellites named Io, Europa, Callisto and Ganymede. Io orbits Jupiter at a distance of 421,000 km (262,000 mi). Europa revolves around Jupiter at a distance of 671,000 km (417,000 mi). Both Io and Europa display signs of volcanic activity. Scientists speculate that hese moons may be able to support primitive life. Ganymede and Callisto are 1,070,000 km (660,000 mi) and 1,883,000 km (1,117,000 mi) away from Jupiter, respectively.

More satellites orbit Jupiter at very large distances. Some of these satellites - named Leda, Himalia, Lysithea and Elara - circle Jupiter at around 11 million km (6,600,000 mi) away. The remaining satellites - named Ananke, Carme, Pasiphae and Sinope - orbit at distances averaging 21 to 23 million km (13 to 14 million mi).