Possibility and Probability

Coding Python and making businesses…

3 February 2006

The line between planet and asteriod

by Nick

With the confirmation of 2003 UB313 being bigger than Pluto the questions of “Is this the tenth planet?” and “Is Pluto really a planet?” have cropped up again. For a long time I was on the side of the fence that said “Just leave Pluto alone, and lets say there are no more planets out there.”. But after reading this article about the differences between planets and asteroids, I’ve changed my mind. I think Pluto should be demoted and the planet count set to 8. In the article Alain Maury points out that if you graph the mass and orbital inclination of the planets and the asteroids (and KBO’s and TNO’s) that something really interesting happens: the two cluster seem to form, one for planets, and one for everything else. Pluto and 2003 UB313 (and several other new discoveries) don’t fall into the planet group, they land in the “asteroid” group. After seeing these charts I’m inclined (har har) to say that unless an object can show by a combination of its mass and orbital inclination that it belongs in the “planet” group, that it is not a major planet. Something tells me that once we are able to explore other solar systems we will probably use that type of a guideline when marking new planets. Of course at some point it won’t matter, the sheer number of objects found across the stars will make it impossible to name and keep track of everything.