Jupiter is the fifth planet in the Solar System, as well as the largest planet in the system. It is a gas giant with a mass slightly less than one-thousandth of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian planets.
Jupiter has multiple moons, at least two of which, Io and Callisto, are inhabited by man by 2158.