Planets and Plutons - IAU Draft Definition

No it says (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape.

err, ok...

I was quoting someone off the MP forum.

I guess its quite interesting, possibly amusing, to see how this debate is going. There are some folks out there arguing the merits of their own definitions like mad.

On a serious note though, if any of the silliness [1] became broad public knowledge, I don't think it would do astronomy any good.

Dave

[1] I'm not of course suggesting anything from this board - just the folks in Prague. Maybe they've all got hangovers so we should cut them some slack...

Here's another great comment.

I'd like to propose a refinement to the argument that Pluto and Charon are in actual fact, two planets, since the barycenter of the two lies outside of either object. Whenever the barycenter passes through one, the other should no longer be considered a planet.

This happens quite often with the Sun. The center of gravity of the solar system (which produces a wobble in the Sun, due mainly to Jupiter) sometimes passes through the Sun, so at those times I propose that it be recognized that the solar system has no planets. Kind of like an on and off switch.

I propose that it be recognized that the solar system has no planets. Kind of like an on and off switch.

I thought you were going to propose that the Sun was a planet there for a minute

I'd like to propose a refinement to the argument that Pluto and Charon are in actual fact, two planets, since the barycenter of the two lies outside of either object. Whenever the barycenter passes through one, the other should no longer be considered a planet.

I think what is also unique about the Pluto+Charon system is that the two appear almost tidally locked. Each appears stationary from the others view on the surface. Thus, they are effectively orbiting each other. Charon isn't exactly orbiting Pluto in the true sense of a satelite.

Hi all,

Saw this article on another forum, its by Prof Mike Brown, discoverer of UB313. He estimates that by the new definition there are 53 planets in the solar system currently. See article below:

www.gps.caltech.edu/~mbrown/whatsaplanet/howmanplanets.html

I'd actually forgotten about Sedna. That surely has to qualify now too.

This is going to get ridiculous. There's going to be so many planets that the only ones of consequence will the the innermost 8 (or is that 9 now). All the rest will only be an afterthought and the average person will probably never know that they are planets. It'll only be of consequence to astronomers - and they'll still just be regular EKBO's to me.