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

[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.