Jupiter is the fifth planet from the Sun and the largest in Sol. It is a giant planet with a mass one-thousandth that of the Sun, but two and a half times that of all the other planets in the Solar System combined. Jupiter has been known to astronomers since antiquity. The Romans named it after their god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough for its reflected light to cast shadows, and making it on average the third-brightest object in the night sky from Earth after Luna and Venus.
As of 2180, small mining colonies have been established on each of the four Galilean moons that orbit Jupiter, as well as a station on Io, the closest moon to Jupiter itself, dedicated to researching the gas giant and its surrounding moons.