Jupiter is the fifth planet located in the Sol system. It is a gas giant with several satellites. Its satellite Io is associated with the transfer point where the primary jumpgate of the Sol system orbits. 
In 2260, after attacking the colony on Ganymede, a crazed Shadow Vessel was lured into Jupiter's atmosphere by White Star 1 under the command of John Sheridan. It was trapped by the gravity well and crushed by the extreme atmospheric pressure. Responding to the colony's distress call, the EAS Agamemnon tracked the ship to Jupiter where it mistook the White Star (a then unknown design) for the "unknown alien vessel" responsible for the attack. Unwilling to fire on his old ship and knowing full well the of the ship's ability to chase them down, at the suggestion of Delenn, the White Star initiated what is thought to be the first successful atmospheric jump to Hyperspace. The massive energy discharge from the Jump point ignited the local hydrogen, making it appear from the Agamemnon's point of view that the alien ship had exploded.