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. It was the first non-spherical moon discovered. 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.