Wednesday, August 16, 2006

News from the world of Classificational Astronomy

The IAU planet definition committee has come up with a new definition of what a planet is. The good news for Pluto partisans is that Pluto gets to stay in! (The cartoon I wanted to link to has vanished, presumably in celebration of this news. Grr.) Of course this highly charged decision has yet to go in front of the full International Astronomical Union to be confirmed. I predict a debate similar to the ones in the 3 Star Wars prequel films [1].

The BBC has a quite good article on it, including the diagram of the new planets, Charon (currently a moon of Pluto), Ceres (currently an asteroid) and UB313 (currently a Kuiper object). In case you can't be bothered to click through: the old definition was that a planet is a celestial body that moves against the fixed stars; the new that it orbits a star, and is not in orbit around another body, and has enough gravity to form a spherical shape.

Not that any of this actually changes the stuff that's out in space. But it may change the way we think about them. And it's cool to have more planets.

Edit: The debate continues, in a much more amusing form, everywhere else on the internet.

[1] Which means I'll probably nip out the room to get a drink while it's happening.