Jupiter

Jupiter is the largest gas giant in the solar system. Despite being a gas giant, by the 31st century, it has apparently become somewhat solid enough to contain a university as well as for Al Gore to volunteer to pick up cans on it.

Moons
Jupiter has the largest amount of moons as any of the planets in the solar system. A notable one is Europa, which has become terraformed by the 31st century, yet remains somewhat deserted.