Introductory Astronomy: The Planet JUPITER

Basic Facts:
Average distance from Sun: 5.2 AU
Period of revolution about Sun: 11.9 years
Period of rotation: 9.8 hours
Radius: 11.2 Earth radii
Mass: 318 Earth masses
Average Density: 1.34 g/cm^3
Magnetic Field: 20,000 times Earth's
Surface features: Giant Red Spot, belts of brown, red, blue-green, and white gas clouds, one thin, faint ring
Atmosphere: 86.1% H2, 13.8% He, < 1% h20, ch4, nh3
Temperature: -262 - (-100) degrees Fahrenheit

Jupiter is a giant planet! Eleven Earths would easily fit across its diameter. It contains about 70% of the planetary matter in our Solar System. Jupiter is thought to have a small, rocky core, surrounded by a thick layer of liquid hydrogen and a thick atmosphere which is mostly hydrogen. The atmosphere of Jupiter is turbulent. It rotates rapidly and has high and low pressure zones which rise and fall. Violent storms are also seen in the atmosphere, for example, the Great Red Spot. Its ring is dark and reddish and thought to be made of silicates.

Unlike the terrestrial planets, Jupiter actually generates some energy of its own (terrestrial planets are powered only by absorbing and reflecting sunlight). While Jupiter is not massive enough to fuse hydrogen, it is contracting under gravitational pressure and thus heating up. Jupiter radiates more energy than it receives from the Sun.

Jupiter has at least 16 moons. The largest (and most well known) are Io , Europa , Ganymede , and Callisto. (A view of Jupiter with its four largest moons.) These moons are rocky, versatile worlds. One has active volcanos, and another has a liquid water mantle. The other moons are very small and some are thought to be captured asteroids which did not form with Jupiter.

To learn more about Jupiter and its moons, click here.