Jupiter, Fifth planet from the Sun, the largest nonstellar object in the solar system. It has 318 times the mass and more than 1,400 times the volume of Earth. Its enormous mass gives it nearly 2.5 times the gravity of Earth (measured at the top of Jupiter’s atmosphere), and it exerts strong effects on other members of the solar system. It is responsible for the Kirkwood gaps in the asteroid belt and changes in the orbits of comets; it may act as a “sweeper,” pulling in bodies that might otherwise collide with other planets. Jupiter has more than 90 identified moons. It has a diffuse ring system that was discovered in 1979 by the Voyager spacecraft. Jupiter is a gas giant, composed mainly of hydrogen and helium in proportions near those of the Sun, which it orbits every 11.9 years at an average distance of 483 million mi (778 million km). Its rapid rotation (9 hr 55.5 min) acts on electric currents to give it the largest magnetic field of any of the planets and causes intense storms, including one that has lasted hundreds of years (the Great Red Spot). Little is known of its interior, but it is presumed to have a deep layer of metallic hydrogen and a dense core. Its central temperature is estimated to be 45,000 °F (25,000 °C); it radiates twice as much heat as it receives from the Sun, probably largely heat left over from its formation.
