Pluto is not a planet.

[bjarvis]

There, I've said it. I'm still dealing with the emotional aftermath of a solar system with only 8 planets, but I can now say it in public.

At best, it's a sizable Kuiper belt object, and an interesting one at that, but Pluto is not a planet.

Comments

[bjarvis.livejournal.com]

Pluto has its moon, Charon, discovered in 1978. It also has two smaller ones found last year. Still, having gravitationally-bound satellites isn't enough to make it a planet... there are asteroids which would fit that bill. In all, Pluto just looks more like a member of the Kuiper belt family than it does a member of the eight inner planets.

The astronomical association has yet to rule one way or another but I'm coming to terms with the probability that Pluto will some day be officially downgraded like GM junk bonds.

[furmuslbulk.livejournal.com]

say it ain't so~

[(Anonymous)]

come to think of it, they DID announce the discovery of a 10th planet last year...

[furmuslbulk.livejournal.com]

come to think of it, they DID announce the discovery of a 10th planet last year...

[bjarvis.livejournal.com]

I think it was informally named Xena (yup, after the warrior princess).
It's the discovery which made the is-it-or-isn't-it-a-planet debate so timely: Xena is larger than Pluto but is definitely in KB space, so either we have to expand our informal definition of planets to include all KBOs, or we downgrade Pluto from planet to large, inner KBO.

There's going to be a lot more discoveries like Xena, Sedna & Quaor in the next few years so we'll either have a much larger sample space on which to base a decision, or we'll have a lot more rewriting of our astronomy texts.