Apparently the IAU general assembly did not take to the definition offered up by their sub-committee for determining what is and is not a planet in our solar system. That’s good news in my opinion. I and others complained about the new “Pluton” category as arbitrary and also confusingly overlapping “dwarf-planet”. A revised proposal reads:
A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid-body forces so that it assumes a hydrostatic-equilibrium (nearly round) shape, and (b) is the dominant object in its local population zone, and (c) is in orbit around the Sun.
Point (b) is almost exactly what was proposed by King Aardvark on his blog and a comment here. Way to go King! This new definition makes Pluto a dwarf-planet, like the largest asteroids, and that suits me fine. It is a member of the Kuiper Belt, and more than a dozen other objects are in the same orbital resonance that Pluto has with Neptune. So, 8 planets, and a whole bunch of dwarf-planets. Unless they change the wording again before Thursday. If I had a vote, I’d support this definition.