OK, let’s take this from the beginning…

In august 2006 the International Astronomical Union decided that Pluto was not worthy of it’s title as a planet because of the discovery of several Pluto-like objects outside the orbit of Pluto, and the fright that we would soon be teaching our kids a list of 50 planets. So they decided that Pluto should henceforth be known as a dwarf planet.

Alright… it may take some getting used to, but we’ll accept it.

But just as we’d all gotten used to the new definition, what could be a better idea then renaming the whole class again? Surely the IAU has nothing better to do? I guess not. Last week the IAU decided that Pluto and Pluto-like objects should now be called “plutoids”, giving Pluto back a lot of seemingly lost credit. I mean who wouldn’t want a whole class of objects named after them? So the official definition of a plutoid is:

“Plutoids are celestial bodies in orbit around the sun at a distance greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighborhood around their orbit.”

Alright, this is all getting a bit confusing to be honest, i mean it’s all semantics after all, there is no real meaning behind these things, it’s just us humans that like to label things. So fair enough, dwarf planets will now be named after the biggest dwarf planet known, Pluto. But hey, what happens then if we discover another large plutoid? As an astronomer in the above linked article points out:

“The only fly in the ointment that I can envision is if a plutoid larger, than, say, Mars is detected,” Laughlin points out. “In that case, I think we’d see a big flare-up of the what-is-a-planet debate.”

So here we are, just waiting for the next big thing in solar system object renaming (exciting, isn’t it?). Meantime a Japanese team of astronomers propose a theory that there may exist exactly such a large object anywhere from 100 to 200 AU from the Sun (one AU is the distance from the sun to earth). This would explain some of the odd things we see in the Kupier Belt, a large belt of icy objects (like plutoids) outside the orbit of Neptune. Seriously, I can’t wait for them to find this. Not only will the discussion be fun to watch, but a whole lot of actually interesting astronomy could be learned from such an object. Like if it has a hot core, there’s the possibility of an under-surface ocean, making it possible for life as we know it to evolve. Especially if the building blocks of life are floating around in space.