Hyperion is a moon of Saturn. It was discovered on September 16, 1848 by William Cranch Bond, George Phillips Bond and William Lassell. It is irregular in shape, and has a sponge-like appearance. It is the second largest irregular (i.e. not spherical) moon in the Solar System, the largest being Proteus. Its rotation is chaotic, meaning its axis of rotation wobbles, unlike how the Earth and the Moon rotate, or any other moon in the Solar System.