good article today about the International Astronomical Union vote that demoted Pluto from planet status.
It was fairly obvious that the previous proposal, last week, that defined "planet" as anything big enough that its gravity made it round, was obviously a red herring that nobody was going to take very serious. Fercryinoutloud, it made the asteroid Ceres a planet, as well as Earth's moon (in a few billion years when it gets a bit farther away from us and ceases to be considered a moon).
But apparently there were several other dirty tricks played by the anti-Pluto faction, and IAU members who weren't able to be in the room at the time of the vote are not happy and are spoiling for a rematch. The new definition doesn't make much more sense than the previous one, anyway: it's based on gravitationally sweeping out objects from an orbit, but that also rules out Earth, Mars, Jupiter and Neptune, all of which have non-satellite objects along their orbits.
And of course the public is pretty upset about it for sentimental, non-scientific reasons. Try searching for Pluto or "Save Pluto" on Cafe Press to see the amazing selection of pro-Pluto merchandise you can buy barely a day after the IAU decision. (Personally, I want a Honk if Pluto is still a planet bumper sticker.)
It'll be interesting to see if the decision sticks.
So do I have a viable definition of "planet" which includes Pluto but not Ceres or the various other Kuiper belt objects which are continually being discovered?
Why, no, I don't. But the discussion is purely semantic anyway. Whether we call Pluto a planet doesn't make any difference to planetary science. But it does make a difference to an enormous collection of textbooks, museum exhibits, and other science-for-the-public displays.
Pluto is big enough to have been discovered in 1930, back in the days before computerized robotic telescopes and satellite imaging; it's been considered a planet for 76 years. There's no scientific benefit to changing that, and a lot of social and political reason not to -- especially now with New Horizons headed there to give us our first up-close look at what Pluto actually looks like.
There are two possible bright notes to the Pluto decision. First, Mark Taylor pointed out that it has become much easier to observe all the planets in one night, even with a very small telescope or binoculars.
And second, maybe Christine Lavin will make a new updated version of her song Planet X and go on tour with it.
[ 22:56 Aug 25, 2006 More science/astro | permalink to this entry | ]