totient | (no subject)

After some thought, I think I'm using the following definition of planet:

An object formed in a protoplanetary disk (http://en.wikipedia.org/wiki/Protoplanetary_disk) (this excludes Oort cloud objects such as Sedna and the interstellar objects Oph 1622), not a star (as a rule of thumb, this means smaller than 14 jupiters), large enough to have had an atmosphere during formation (as a rule of thumb, this means larger than the moon), and not in the gravitational influence of another planet (I mean this to exclude not just moons but also plutinos (http://en.wikipedia.org/wiki/Plutino), though in our particular solar system plutinos are all excluded by the size restriction anyway).

Under this definition, 2003 UB₁₃ almost qualifies, but not quite. Oph 1622 does not, because it doesn't appear to have formed in a proplyd.

There are plenty of other definitions out there, and many of those are at least more concise; the purpose of this poll was to present a bunch of corner cases and see how people's perceptions of the objects affect the validity of the various definitions out there.

I think your definition is too restrictive, and inapplicable. I doubt we can really say enough about how planets formed, to be able to use that as a definition. For example, suppose you found a rocky body out in the Kuiper belt, in an eccentric orbit? Would you propose that it had formed in the proplyd and got ejected, and so was a planet, while its neighbours were not?

I am more inclined to call just about anything whose shortest orbital period is around a star, a planet, and to accept a range of subtypes. Gas giants, rocks, snowballs, Trojans,...

It's a planet if it was in My Little Golden Book of Planets?

(of COURSE I'm joking.)