Haumea (designated as 136108 Haumea) is a dwarf planet, located beyond Neptune's orbit. Just one-third the mass of Pluto, this dwarf planet was discovered in 2004 by a team headed by Mike Brown of Caltech at the Palomar Observatory in the United States. On September 17, 2008, it was recognized as a dwarf planet by the International Astronomical Union (IAU).
Haumea's extreme elongation makes it unique among known dwarf planets. Although its shape has not been directly observed, calculations from its light curve suggest it is an ellipsoid, with its major axis twice as long as its minor. Nonetheless, its gravity is believed sufficient for it to have relaxed into hydrostatic equilibrium, making it a dwarf planet. This elongation, along with its unusually rapid rotation, high density, and high albedo (from a surface of crystalline water ice), are thought to be the results of a giant collision, which left Haumea the largest member of a collisional family that includes several large trans-Neptunian objects (TNOs) and its two known moons, Hi'iaka and Namaka.