NASA's PR machine is gearing up to announce today the discovery of Sedna, a Pluto-like object way the hell out in the Kuiper belt, the farthest solar system object yet found, etc.

This will of course spark the usual debates over whether Sedna is really a "planet", whatever that means. The definitional problem, as expressed in terms of Pluto, has generated undless debate. My suggestion is that we stipulate that Sedna is a planet, given that its characteristics are as planet-like as Pluto's, but primarily because that makes the whole thing a lot more fun. A tenth planet! How cool is that?