Jupiter is the largest planet in the solar system, bigger than all the other planets combined. It is the fourth brightest object in the sky, after the Sun, Moon, and Venus. As the fifth planet in the solar system, it lies on the far side of the Asteroid Belt and is the gas giant planet closest to Earth. Jupiter is named after the king of the Roman gods. Jupiter takes about 12 years to orbit the sun and rotates in about 10 hours. This short Jupiter "day" is amazing since the planet is roughly 11 Earth diameters wide.
Unlike the rocky planets, Jupiter is a ball of dense hydrogen, helium, water, nitrogen and other gases over a tiny rocky core. Powerful winds dominate the atmosphere with criss-crossing jet streams, lightning and huge hurricane-like storms like the Great Red Spot. This storm has been raging for over 300 years and is about 2 Earth diameters wide. The Great Red Spot can be seen on Jupiter along with four moons: Io (smallest), Europa, Callisto and Ganymede in this NASA image.
The planet had 39 known moons at the time of this image and a slight ring of smoke-sized particles and dust. The planet contains 71% of the planetary matter in the solar system and so its huge gravity pulls every object toward it. In fact, most of its moons were captured rather than forming with Jupiter. Scientists watched in awe as comet Shoemaker-Levy 9 broke up and smashed into Jupiter making explosions the size of the Earth.
Jupiter's main ring system is formed by dust kicked up as interplanetary meteoroids smash into the giant planet's four small inner moons Almathea, Thebe, Adrastea and Metis. The ring system begins about 92,000 kilometers (55,000 miles) from Jupiter's center and extends to about 250,000 kilometers (150,000 miles) from the planet. NASA's Voyager 2 detected an uneven dust ring around Jupiter in 1979. One Voyager image seemed to indicate a third, faint outer ring. The Galileo spacecraft found a flattened main ring and an inner, cloud-like ring, called the halo, both composed of small, dark particles, and a third ring known as the Gossamer Ring. The third ring is actually two very thin rings made up of debris from Amalthea and Thebe. Unlike Saturn's rings, there are no signs of ice in Jupiter's rings.