Fight for Pluto !, A Campaign to Reverse the Unjust Demotion Options

[mars loon]

Dear Friends,

Today I am extremely dissapointed that the Pluto Demoters have triumphed.

I respect their opinion, but disagree with it.

I strongly agree with Alan Stern's statement calling it "absurd" that only 424 astronomers were allowed to vote, out of some 10,000 professional astronomers around the globe.

This tiny group is clearly not at all representative by mathematics alone.

I believe we should formulate a plan to overturn this unjust decision and return Pluto to full planetary status, and as the first member of a third catagory of planets, Xena being number two. Thus a total of 10 Planets in our Solar System

Please respond if you agree that Pluto should be restored as a planet.

ken

Ken Kremer
Amateur Astronomers Association of Princeton
Program Chairman

[David]

If it had been up to me, personally, to make a decision on the matter, I would probably have minimally dubbed 2003 UB313 a planet, drawn a lower size limit at 2250 km, and left it at that. If I thought the world was ready for a more meaningful set of designations, I would have mandated breaking up the "planet" group into at least three groups, and maybe more, that were to be considered at least as different from each other as they are from asteroids. I would not have taken any criteria into account other than mass and diameter, and although I probably would not have relabeled large satellites as "planets", I would have provided for a parallel set of divisions for satellites.

However, it wasn't up to me, and I have to say that the only thing seriously wrong with the IAU decision is the "neighborhood clearing" language, which is too obscure to even be useful. It's fair to say that some large objects exert a gravitational influence on smaller objects in their surroundings, which if not as continuous as their influence over their satellites, is in some way comparable. We can certainly say that Jupiter's Trojans are in Jupiter's gravitational sphere of influence, and in a different way Pluto is under the influence of Neptune. I doubt that such spheres of influence can be extended to include every single asteroid and KBO, except in the most general sense, in which all the planets (particularly the giants) have non-negligible influence on the orbits of the others (Neptune's perturbations of Uranus' orbit being a famous example). But we don't want to conclude that Jupiter is the only planet in the Solar system -- doubtless for sentimental and unscientific reasons! I am not sure that even a better definition of what is meant by "orbit clearing" is going to clean this up; if we regarded the orbits of all Solar system objects as alike, without regard to the mass of the objects, I doubt that the "major planets" could be easily picked out of the crowd.

Other than this problematic limitation, I am not terribly perturbed by result of the decision; it was one reasonable decision out of many possible reasonable decisions. I don't think it was the wrong decision; but that doesn't mean that I think it was the right one. I think the real mistake here is to suppose that there are absolutely right or wrong decisions on a topic like this; it's certainly not a moral question, and "Pluto is a planet" is not a statement that can be determined to be true or false in the way that "Pluto has a diameter of c. 2300 km" can be. The category of planet doesn't exist in nature; it's a creation of the human mind, and only has meaning relative to what humans want to make of it.

I don't expect this to be the last word on the question; I think that additional information about the nature of the Solar system, while not fundamentally changing the various rationales used by planetarians and antiplanetarians, may well change the emotional relationship people have to the word "planet". I appreciate that people may have strong feelings on either side of the question, but at present I'm happy to let those people engage. The result of the IAU vote reflects, I think, more politics than science; the antiplanetarians were better organized, more unified, and more passionate than the planetarians, and arrived in Prague prepared to win. Now the planetarians have got a Cause of sorts, and they will have three years to organize before they go off to Rio de Janeiro. Perhaps at that time they will be in a better position - and perhaps not. Public reaction -- especially the public consisting of professional and amateur astronomers -- to the decision is likely to play a role. If people cannot be bothered to do anything but laugh at the decision, then it is likely to stick. If it's generally rejected by ordinary people who have an interest in astronomy, then the IAU may merely have discredited itself. It promises to be an interesting time.