The New York Times offers a feature story (free registration required) on Caltech scientist Michael E. Brown, who used Palomar data to find 2003 UB313, the Kuiper Belt object thought to be larger than Pluto. Working with David Rabinowitz of Yale and Chad Trujillo of Hawaii’s Gemini Observatory, Brown is also behind the discovery of Quaoar and Sedna, substantial KBOs in their own right, but not of planetary dimension (although just what constitutes a planet is, inevitably, a focus of the article).
Brown on the terminology debate: “If people want to get rid of Pluto, I’m more than happy to get rid of Pluto and say this one isn’t a planet, either,” Dr. Brown said. “If culturally we would be willing to accept a scientific definition, that would be great… The only thing that would make me unhappy is if Pluto remained a planet, and this one was not one.”
Centauri Dreams‘ take: The simple solution is to declare anything Pluto-sized and up a planet, although it opens up the possibility that we will soon discover even more worlds that fit this definition. Nonetheless, de-throning Pluto from its planetary designation would be an even more arbitrary imposition that few in our society would accept. We may just have to get used to the fact that our Solar System is larger and far more varied than we thought.