Who cares if Pluto is a planet?

| Comments (3) |
Google News has 800+ articles on the question of whether or not the IAU is going to demote Pluto from planet to asteroid. Apparently they've decided to upgrade three other objects instead:
Among the chosen few within the solar system would be not only Pluto, whose status has been challenged in recent years, but also Ceres, the largest asteroid; 2003 UB313, nicknamed Xena, an object discovered by Dr. Brown in 2005 orbiting far beyond Pluto in the outer solar system; and even Plutos largest moon, Charon.

In addition, at least a dozen more solar system objects are waiting in the wings for more data to see if they fit the new definition of planethood, which is that an object be massive enough that gravity has formed it into a sphere and that it circles a star and not some other planet.

The definition, they said, would apply both inside and outside the solar system.

The new definition was to be announced today in Prague, where some 2,500 astronomers are meeting in the triannual assembly of the International Astronomical Union. It is the work of the groups Planet Definition Committee, whose chairman is Owen Gingerich, a Harvard astronomer. The astronomers will vote on the definition on Aug. 25.

In a statement, Dr. Gingerich said this might not be the last word on what a planet is. Science is an active enterprise, he said, constantly bringing new surprises.

Maybe I'm missing something important here, but this seems to be a pretty clear case of map/territory confusion. As I understand it, we basically agree on the characteristics of Pluto and Charon, the question is just whether we call them planets or not. Does this affect anything? I mean, it's not like people on Charon are suddenly going to be the recipients of federal aid because Charon is now a planet. And how does the rest of the Kuiper Belt feel about it?

For that matter, what's this stuff about science being an active enterprise. Exactly what scientific discoveries would lead us to decide whether being round is part of the definition of being planet?

3 Comments

The IAU release states that Pluto will remain a planet, but be classified as a pluton. Also, check out the quote from Dr. Gingerich where he mentions the "vigorous discussion" around the definition of a planet. Fascinating stuff. So I guess I am saying I care, or at least I am interested enough to spend an hour posting and commenting on it.

I don't know, it just strikes me as odd to posit that Ceres and Pluto/Charon are likely the same class of object, i.e., formed in the same manner or composed of similar elements/densities. In addition, if you're going to say that Charon and Pluto are a binary system, which does seem to be the case, then how can you ignore the two other bodies in that system which orbit the same barycenter? Like you, I find "round" to be a rather arbitrary distinction at that distance.

This exercise strikes me as design by committee: "I'll trade you one Pluto for one Ceres..."

I would prefer to see Pluto and Charon designated as Trans-Neptunian Objects, along with UB313 and whatever else sits in the general vicinity between Neptune and the Oort Cloud, and I would not count Ceres (or any other of the inner planetoids) in the same vein. Call them "plutons" for all I care, but call them something else. NASA's Dawn mission (set to launch next summer to rendezvous with Vesta in 2011 and Ceres in 2015) ought to give us enough data to figure out what to call Ceres.

I'm with Ekr. This is a big deal only because lots of kids memorize mnemonics for the planets etc.

Leave a comment