Jupiter

Jupiter is the fifth planet from the Sun and the largest planet in the Solar System. It is a gas giant with no solid surface, composed mainly of hydrogen and helium, and is so massive that it contains nearly 2.5 times the mass of all the other planets combined. Its diameter is about 11 times that of Earth, and it orbits the Sun at an average distance of 5.2 astronomical units, completing one revolution in 11.86 years.

The planet’s rapid rotation, which takes just under 10 hours, gives it an oblate shape with a noticeable equatorial bulge. Jupiter’s visible atmosphere is arranged in colorful latitudinal bands, where strong winds and turbulence produce powerful storms. The best-known of these is the Great Red Spot, a giant storm observed since at least the 17th century. Beneath the atmosphere, Jupiter is thought to contain a deep layer of fluid metallic hydrogen and a dense interior core. Heat from ongoing contraction makes the planet emit more energy than it receives from the Sun.

Jupiter has the strongest magnetic field of any planet in the Solar System and an extensive magnetosphere. At least 115 moons are known to orbit it, including the four large Galilean moons—Io, Europa, Ganymede, and Callisto—which were first observed by Galileo Galilei in 1610. Ganymede is the largest moon in the Solar System and larger than Mercury. Jupiter is also surrounded by a faint ring system made mostly of dust.

Visible to the naked eye, Jupiter is usually the third-brightest natural object in the night sky after the Moon and Venus, and it has been known since prehistoric times. Its name comes from Jupiter (god), the chief deity of ancient Roman religion.