Haumea

The fast rotating dwarf planet, Haumea (artist's impression)
Credit: Stephanie Hoover

Haumea (pronounced how-may-a) is a rugby ball-shaped dwarf planet that was discovered in December 2004.

It orbits the Sun at an average distance of 43.1 astronomical units (AU), but can reach as close as 34.7 AU and as far out as 51.5 AU. Haumea completes one orbit or the Sun every 283 years.

It's around one-third the mass of Pluto. We've never taken close observations of Haumea, but because of the way it reflects sunlight astronomers think that it's shaped like a rugby ball, with one of its axes twice as long as the other. The odd shape is caused by its very fast rotation rate - it spins once every 4 hours.

Haumea has two known moons, named Hiʻiaka and Namaka, and the surface temperature on all three is thought to be around -240°C (or 32K).

Haumea is also a type of plutoid - a dwarf planet that circles the Sun beyond the orbit of Neptune.