Jupiter
From Gineipaedia, the Legend of Galactic Heroes wiki
Jupiter is the fifth planet in the Sol Starzone. It has four large moons, Callisto, Europa Ganymede, and Io. Io was the site of a United Earth Government outpost and served as the launch-site for many UEG deep-space expeditions, including the Alpha Centauri Expedition and the early tests of Warp technology.
