The key provision of the twice-revised definition reads as follows: "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." (For now astronomers are trying to define what "planet" means only in our own solar system, avoiding the complication of planets around other stars or, worse, floating in free space.)

Supposedly b is what kicks out Pluto. What constitutes a local population zone? Pluto is the dominant object within 1 AU of it's orbit. If we define a zone that wide as standard then Mercury and Mars are not planets and Venus would then be on the cusp. That's just stupid. Make it 5 AU wide and Pluto probably would still be a planet, but none of the terrestrial planets would. b should be replaced by coorbital to rule out Charon and other large satellites, not left as is and arbitrarily applied to Pluto. It's also ridiculous to use this against Ceres. It clearly is the dominant object in the asteroid belt.

It's sad to see a plurality of Astronomers against sound rigorous definitions simply to fit an emotional opinion about whether a particular object is a planet or not.

Regards,
MArk