Haumea

Haumea is the fifth official dwarf planet in our solar-system. The four before it are Pluto, Eris, Ceres & Makemake. It was classified as a dwarf planet in September 2008. It is a large Kuiper Belt Object (KBO). It was labelled 2003 EL61.
Haumea is also very cold & icy (the temperature is about -241°C). It orbits the Sun from the far edge of the solar-system too & it takes 285 Earth years to orbit it just once. Usually it is farther from the Sun than Pluto.

Haumea is smaller than Pluto & Eris and it has an odd shape... This odd shape is because the planet is spinning so fast that it is pulled into an ellipsoid (a 3D ellipse). Haumea is 1,960 km across measured from the farthest ends & only about half of that (996 km) from the nearest points across. Therefore also, the days on Haumea are very short. They are less than 4 hours on Earth! It is also dense, which means, most of it is probably just made up of rocks.
Most of the other KBOs probably has more ice on them than Haumea. It has two known moons (like Mars), which were both discovered in 2005. They are called Hi'iaka & Namaka.

Astronomers think that Haumea crashed with another object a long time ago. That would be another reason for the weird shape & also why it spins so fast. The collision might also have caused much ice on Haumea to fly away, so there is less ice now. Its moons may be just some leftovers from the crash.
There are two different groups that might get the credit for discovering this planet. One groups is led by Mike Brown of the California Institute of Technology. The other group is led by José Luis Ortiz Moreno from the Sierra Nevada Observatory in Spain. Haumea was discovered between March 2003 & July 2005. Before it was called Haumea, while it was still coded, it was given the nickname "Santa" by Brown's group because they discovered it around Christmas 2004.
In the Hawaiian mythology, Haumea is the goddess of fertility & childbirth. She had three children named Hi'iaka (Hawaiian sea goddess), Namaka (goddess of hula dancers) & Pele (Hawaiian goddess of volcano & fire). This is where the two names of its moons come from.