Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass one-thousandth that of the Sun, but two-and-a-half times that of all the other planets in the Solar System combined. Jupiter has been known to astronomers since antiquity. It is named after the Roman god Jupiter. When viewed from Earth, Jupiter can be bright enough to cast shadows, and is on average the third-brightest natural object in the night sky after the Moon and Venus. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, though helium only composes about a tenth of the number of molecules in Jupiter.
It is about 778 million kilometers (1.3 AU) from the Sun.
Jupiter completes one orbit around the Sun (a year in Jovian time) in about 11.86 Earth years (4,332.6 days).
Jupiter has a day of about 9.9 hours.
Jupiter has 62 moons. The largest moons are Io, Europa, Ganymede, and Callisto, which are referred to as the Galilean satellites. Io is the most volcanically active body in the Solar System. Europa is thought to have a subsurface ocean of liquid water. Ganymede is the largest moon in the Solar System, and Callisto may have a subsurface ocean of brine.
Jupiter has a faint ring system composed of dust particles ejected from its moons. Jupiter is also the source of the most intense radiation environment in the Solar System.