Jupiter is the largest planet in the solar system. It is composed primarily of hydrogen and helium gases and has 67 known moons. Some key facts about Jupiter include that it is located about 750 million km from the sun, has a rocky core below its compressed hydrogen layers, and has four largest moons called Io, Europa, Ganymede, and Callisto that vary in size and orbital characteristics. NASA has explored Jupiter since the 1970s through missions like Pioneer, Voyager, and Galileo to learn more about its rings, moons, and composition.