Twin City Amateur Astronomers


  Earth, the Blue Planet
Overview Facts and Figures Missions to Jupiter Moons
Jupiter is the largest planet in the solar system, the fifth planet from the Sun.

It orbits the Sun every 12 year and revolves around its axis in an astounding 10 hours!

Jupiter is composed of gas, primarily hydrogen. Its atmosphere contains ammonia, methane and other simple chemical compounds that give rise to the colored bands in its surface layers.

Jupiter has many moons, but four of them are notable because they are so large. Callisto, Ganymede, Io and Europa are among the largest moons in the solar system. These four were observed by Galileo when he turned his telescope to the heavens and these four moons are refered to as the "Galilean" moons. They are easily visible through a small telescope as they orbit Jupiter.