Re: "Pluto Now Called a Plutoid"

Erik Max Francis wrote:
Brett Paul Dunbar wrote:
No that is actually totally wrong. The definition is entirely
unambiguous, given the sheer size of the gap. On either the
Stern-Levinson parameter or Soter's Planetary discriminant, the gap is
about five orders of magnitude.

Neither of these measures is mentioned, even indirectly, in the IAU's resolution regarding Pluto or any subsequent IAU resolutions. So, so what?

They don't mention any other specific method of measuring neighborhood-clearing either. Or several other potentially ambiguous parts of the definition, such as what it means to be "orbiting the sun" (there are various co-orbital bodies that could go either way if you play with the definition a bit). I think they assumed that most people reading their resolution would not be trying to lawyerly nitpick holes in it but would instead be more interested in the basic spirit it conveyed.

Do you know of any methods of quantifying "neighborhood-clearing" that don't make the division between Pluto and the rest obvious?

Why not assume that they intend one of the previously-published methods that _do_ make this division obvious, since they explicitly say in the resolution that it makes that division? Do you have some reason to believe that they picked an ambiguous definition and then made an arbitrary decision to exclude Pluto?

The number of objects classified as planets was small enough that it was
possible to list all the known objects that meet the criteria, listing
examples can be useful and there are only eight known so it was entirely
practical to list all of them. The definition of a Dwarf planet on the
other hand is far less clear for example Vesta appears to have become
spherical, solidified then been distorted by as massive impact, it is
unclear whether that is a dwarf planet or a small solar system body.

You're making my point for me.

The only thing being called into question as imprecise here is the distinction between dwarf planets and small solar system bodies, not the distinction between planets and dwarf planets.

In the real-life solar system there's a smooth continuum of examples from "almost perfectly round" to "not at all round", so it's to be expected that there'll be fuzzy edges if you base a definition on that characteristic. Orbital cleanliness, on the other hand, shows a large discontinuity between the eight biggest objects of the solar system and all the rest of the swarming masses. So using that as a criterion is much clearer.

Stern's objections are more terminology than content, the IAU definition
matches what he calls an überplanet, clearly he finds the class itself
useful even if he isn't happy about the name.

So the references you're using to back up the IAU disagree with the IAU's resolution and new classification system. Ironic.

Bwah? The division given in the Stern and Levison paper agrees exactly with the results of the IAU's resolution, dividing solar system objects along the same line that the IAU did. It's only the words used to label the resulting groups that differs, as Brett said. Which reference did you think he was using?

The Stern-Levison paper is at http://www.boulder.swri.edu/~hal/PDF/planet_def.pdf in case anyone's new to this iteration of the debate.
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