Jupiter is the third brightest object in the night sky Jupiter is the third brightest object in the night sky. Its orbital period is 11.9 Earth years. Its semi-major axis is 5.20 A. U. (778,000,000 km).

Jupiter is orbited by many moons Jupiter is orbited by many moons. The four largest are called the Galilean Moons.

Mass: 1.9 x 1030g (318 Earth masses) This is more than twice the mass of all the other planets combined. Our solar system is a two object system with some debris.

Radius: 71,400 km, 11.2 Earth radii. It would take 1400 Earths to equal Jupiter’s volume.

Average Density: 1. 3 g/cm3 (Earth’s is 5. 5) Average Density: 1.3 g/cm3 (Earth’s is 5.5). This density is the result of Jupiter being composed primarily of hydrogen and helium.

The different latitude zones rotate at different speeds The different latitude zones rotate at different speeds. This is called differential rotation.

The magnetosphere rotates at the same speed as the areas near the poles: 9 hr 56 min. This is the fastest rotation rate of any known solar system object.

The equatorial regions rotate even faster: 9 hr and 50 min The equatorial regions rotate even faster: 9 hr and 50 min. This rapid spin rate causes Jupiter to be 6.5% fatter at the equator than at the poles. The term for this difference in diameter is oblateness.

Jupiter is believed to have a small, dense, rocky core; about the size of the Earth itself.

Jupiter has an axial tilt of only 3°, and its orbit is very nearly circular. There is very little seasonal change.

Exploration: Jupiter was visited by Pioneer 10(1973) and Pioneer 11(1974) and Voyager 1 & 2(1979). Galileo visited in 1995.