2003 EL61 finally has a name: Haumea.

Artist's conception of Haumea, with its moons, Hiʻiaka and Namaka

Haumea is another new name to remember along with Makemake and all the rest as we find more and more planetary-sized objects in the Solar System. I've decided that I'm going to call anything that orbits a star and has hydrostatic equilibrium (= the spherical shape planets get from having sufficient gravity, as opposed to asteroids which have irregular shapes because their gravity is so low) a planet, because all that business about 'clearing the orbit' is never going to be established in other solar systems as we discover smaller and smaller planets out there too. How are we going to know if something slightly smaller than the Earth orbiting another star has cleared its orbit or not? Let's just agree that the Solar System is bigger than we thought and we actually have a lot of planets.

Here's what's interesting about Haumea:

Haumea is exceptional because its two moons provide the means to also directly determine the mass of the system from Kepler's third law, as the periods of the moons' orbits are determined by the masses in the system. The estimated mass is 4.2 × 10²¹ kg, 28% the mass of the Plutonian system. Because Haumea rotates roughly once every four hours, faster than any other known body in the solar system larger than 100 km in diameter, it should be distorted into a triaxial ellipsoid.

So now that the new (dwarf) planets all have names, here they are again with their moons if applicable:

• Eris
• Makemake
• Haumea
• Sedna
• Orcus
• Quaoar
• Varuna