Hyperion, one of the moons of Saturn, photographed by Voyager 2, 1981.
© National Aeronautics & Space Administration / Science & Society
Saturn has a large number of moons, 18 of which have been officially named. Hyperion, the 16th of these is the largest known irregulaly shaped object in the Solar System. In common with most of Saturn's moons it is largely made up of water ice, and is thought to be a piece of a larger body destroyed by a collision. NASA's two Voyager spacecraft were launched in 1977 to explore the planets in the outer solar system. Voyager 2 pased Saturn in August 1981, before continuing on to Uranus and Neptune.