First, I propose that anything large enough to be spherical or nearly so under its own gravitation, and orbiting a star, should be termed a planet. This is a rough concept that I think most people can agree with.
Second, if any body that would otherwise be called a planet is orbiting another body that would otherwise be called a planet AND the barycenter is outside of either body - then we have a double planet. Case in point: Pluto and Charon. Simple enough.
Third, if any body that would otherwise be called a planet is orbiting another such body, but the barycenter is within one of the two, then the body containing the barycenter is the planet and the other body is a moon of that planet. Case in point: Earth and Luna.
Fourth, any body that is not spherical or nearly so under its own gravitation, but orbits a planet, is a moon of that planet.
Fifth, any body that is not spherical or nearly so under its own gravitation, but orbits a star, is an asteroid.
We will assume that all these bodies are natural and not artifacts, so that excludes space stations, lost spacesuit gloves, communications satellites and Death Stars.
Now, we only have to agree on how spherical something must be and we have instantly resolved all the problems. We ignore what other stuff might be in an orbit (whee, Earth is a planet again!) and we ignore the "dwarf planet" concept. After all, how "dwarf" does it have to be? This is an artificial distinction that really plays havoc with the whole idea of defining a planet at all. Just picture "world's tallest midget" and you see how ludicrous the concept is.
In my opinion (and this is just that, my opinion) it is clear that the IAU wanted to exclude Pluto for whatever reason, and any new bodies in the Oort or Kuiper belt, and so for a personal whim they truly screwed up the definition process. The idea of having to name a whole bunch of new planets probably irritated somebody and we are just fresh out of mythological figures to work with.
A number and letter catalog code is just fine for something we will likely never see or build a McDonald's on within the next twenty years.
Comments? Disagreements?
