Jupiter

Jupiter's Rings

*The distance is measured from the planet center to the start of the ring.

Jupiter's Moons

Nearly four centuries ago Galileo Galilei turned his homemade telescope towards the heavens and discovered three points of light, which at first he thought to be stars, hugging the planet Jupiter. These stars were arranged in a straight line with Jupiter. Sparking his interest, Galileo observed the stars and found that they moved the wrong way. Four days later another star appeared. After observing the stars over the next few weeks, Galileo concluded that they were not stars but planetary bodies in orbit around Jupiter. These four stars have come to be know as the Galilean satellites.

Over the course of the following centuries another 12 moons were discovered bringing the total to 16. Finally in 1979, the strangeness of these frozen new worlds was brought to light by the Voyager spacecrafts as they swept past the Jovian system. Again in 1996, the exploration of these worlds took a large step forward as the Galileo spacecraft began its long term mission of observing Jupiter and its moons.

Twelve of Jupiter's moons are relatively small and seem to have been more likely captured than to have been formed in orbit around Jupiter. The four large Galilean moons, Io, Europa, Ganymede and Callisto, are believed to have accreted as part of the process by which Jupiter itself formed. The following table summarizes the radius, mass, distance from the planet center, discoverer and the date of discovery of each of the moons of Jupiter: