Although it doesn’t really matter what they are called — every classification is more or less arbitrary, and every object is unique in its own way — it is good to have astronomical objects classified anyway; for example, if someone says you that an object is a plutino, and you know what ‘plutino’ means, you immediately understand that it is like Pluto a Kuiper Belt object in 2:3 orbital resonance with Neptune.

The new objects seem to be slightly blurring the line between planets and KBOs. Not only is one larger than pluto, but one also has its own moon very much along the lines of Charon.

When is the IAU going to realize that existing definitions of “Planet” are totally arbitrary, beurocratic designations?

There are already three different classes of planet in our solar system. There are the inner “terrestrial” planets, the big gas giants Jupiter and Saturn, and the two smaller “icy” gas giants, Uranus and Neptune.

When pluto was discovered, the Kuiper Belt as a whole hadn’t been. So, without truly understanding it, they classified it as a “planet”. Now, after the discoveries of objects like Quaoar and Sedna, the KBOs like Pluto are getting a new designation because of their distance and orbital eccentricities/inclines.

But with these truly large worlds, some with moons, are we simply going to have to create a whole new class of planet? What if we were to discover something slightly larger than 2003 UB313 a little bit futher out? What if the orbit was also inclined, which would explain why it hadn’t been discovered yet, but also less eccentric? What if it had an orbit around the same, or slightly less, eccentricity than Pluto? How would we classify it?

Is it maybe time to designate a new classification of “Kuiper Planets”?

I think UB313 should be called a planet if it indeed is bigger than Pluto and also travels closer to the sun occasionally.