concerning the recent (Aug 2006) IAU definition of "planet"
by Juan Antonio Revilla

Date: Thu, 24 Aug 2006 09:53:08 -0600
Subject: Re: [Centaurs] IAU Vote

>I do not understand why it is written everywhere that astronomers stripped Pluto of planet status when it was decided that Pluto belongs to dwarf planets category? Dwarf planet is also a planet, or I am an idiot?

Press releases normally contain errors... or are full of them.

>"Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's."

Pluto's distance shifts with Neptune have nothing to do with it. It is the presence of hundreds or thousands of orbital clones or "orbital impersonators" in its vicinity --the plutinos-- what disqualifies Pluto as a major planet.

>Now, two of the objects that at one point were cruising toward possible full-fledged planethood will join Pluto as dwarfs: the asteroid Ceres, which was a planet in the 1800s before it got demoted, and 2003 UB313...

Not 2, but everything in-between Ceres --or any other nearly spherical or speroidal asteroid no matter if it is smaller than Ceres-- and Pluto and UB313, that is about 12 or 15 bodies already known, plus many others that will be found soon.

>Charon, the largest of Pluto's three moons, is no longer under consideration for any special designation.

That the Charon/Pluto pair is a binary object because their barycenter is outside of the 2 bodies needs not any special voting or IAU proposition. It could have never been considered a separate "planet" in the first place...



Date: Sat, 26 Aug 2006 13:06:51 -0600
Subject: [Centaurs] the IAU resolution -- politics, not science

I would like to take this opportunity to express my personal opinion on the recent IAU resolution.

I liked the original IAU proposal very much and I am sorry it didn't pass... I hope the time will come when it or a very similar one will.

The objects like Pluto were to be called "plutons" (or whatever) based not on dynamics alone (like the "plutinos") but on physical characteristics.

The plutons were planets of the "icy dwarf" type, and included everything beyond the orbit of Neptune that had reached hydrostatic equilibrium so as to be nearly spherical. Then you had the "gas giants" and the the rocky or "earthly" planets --which constituted the 8 "classical planets", and then the rocky dwarfs like Ceres.

This meant that the list of planets would grow considerably, but the gang who had the vote in Prague were not willing to take such a conceptual leap and improvised a new resolution of their own.

I think the proposal that was voted is worthless, because instead of providing a clear scientific definition (in other words, a simple convention reflecting scientific principles) of the word "planet", it left the door open to more confusion and controversy about what is a planet and what isn't. This resolution won't last long.

The resolution that came out shows how jealousy, prejudice, and political and financial concerns dominate Science --as much as everything else, (including Astrology). The original proposal was the result of 2 years work by a comission of specialists. But their work was trashed and largely ignored ... they must have assumed that its members were a bunch of ignorants who did not do any work during those years and did not know what they were doing.

The discoverer of UB313, Mike Brown, represents this last point of view. He assumes lightly and irresponsibly that the proposal the commission came up with was the result of wanting to keep Pluto in the "planet" category at all costs (it isn't a planet anymore officially), stepping over what the comission had unanimously expressed, and practically calling them liars.
Most people might think that a proposal to suddenly go from 9 to 53 planets would have no chance of passing, but I give this one good odds of passing the IAU vote. Why? It sounds scientific, it saves Pluto, and it suddenly makes many more people discovers of planets. Of course, it does even greater damage to the popular concept of the word planet by suddenly adding 44 new ones, all of which are so small that they could easily fit all together inside the earth's moon (which, of course, doesn't count as a planet) with plenty of room to spare, but perhaps that's a small price to finally have a definition after all of this time

this, to me, is missing the point completely because all those 53 or 100 or whatever their number would be within their own planetary sub-category; this is politics and prejudice, not Science.

I would like to quote the words of Owen Gingerich, chair of the IAU Planet Definition Committee, posted from Prague a few days before the voting took place:

Just to keep the record straight, there was absolutely no effort "to keep Pluto an 'official' planet."  Our planet definition committee decided it would be completely arbitrary to draw a line to keep Pluto as a planet, or to draw a line to exclude Pluto as a planet.  We tried to work on scientific and physical principles, namely to decide on the basis of whether self-gravity was enough to pull a body into a roughly spherical shape.  However, because Pluto is so small (1/400 the mass of the earth and smaller than the moon) and its inclination and eccentricity make it clearly a different category of planet, we have proposed a new category with the name "plutons."  This category will grow, and might become rather large.  Just accidentally Pluto continues to be a planet, but no longer a major player apart from being the prototype of the new group.  It is the eight "classical planets" that really dominate the solar system.

later on, after the voting, Gingerich wrote this:

I am very disappointed in the outcome, which deviates mightly from the carefully honed resolution unanimously proposed by the IAU planet definition committee.

You may say that he is simply saving face --and according to many like Brown, he is lying. But in my opinion the Commitee had come up with a proposal that was revolutionary, while the bunch of astronomers who voted in Prague were --in my opinion-- too narrow and conservative and lost the opportunity to take the leap.



Date: Sat, 26 Aug 2006 15:59:46 -0600
Subject: [Centaurs] the IAU resolution -- politics, not science - 2

The discoverer of UB313, Mike Brown, represents this last point of view. He assumes lightly and irresponsibly that the proposal the commission came up with was the result of wanting to keep Pluto in the "planet" category at all costs (it isn't a planet anymore officially), stepping over what the comission had unanimously expressed, and practically calling them liars.

Here is another quote from Brown's web page to subtantiate what I wrote:
"The astronomical union isn’t helping matters by forcing a Hobson’s choice: stick with the current nine planets or open the floodgates to a yawn-inducing 53 or more. It’s a “No Ice Ball Left Behind” policy."

my comment: this is a gross mis-representation of the IAU proposal, which consists of a new and different classification, a new way of categorizing. It has little to do with "No Ice Ball Left Behind policy" --that's Brown's distortion. There's nothing yawn-inducing, this is prejudice and missing what "classification" means, something the IAU proposal was trying to clarify. Why is having 53 "icy dwarfs" or 15 "plutons" yawn-inducing and for whom?

It is a remarkable fact that the proposal was decided upon unanimously by the committee. For the record, here is the original draft:

and here is a picture and who's who of the Planet Definition Committee:



Date: Sun, 27 Aug 2006 03:47:35 -0600
Subject: [Centaurs] the IAU resolution -- politics, not science, 3

>Michael Brown almost literally wrote:
>1) if politics wins out, then we will go to 53 'planets' because more people want to be discoverers of planets.
>2) if science wins, then Pluto should be stripped of its status as 'major planet' and we will go back to 8
>....and then also mentioned a few 'in between' solutions.
>So , I wonder how you now come to the conclusion that politics has won, seeing that it is the second option that prevailed? -

And you believe him? I think it is exactly the opposite of what he is saying and have explained my reasoning in 2 posts.

It is one thing to express your opinion about an issue, but he --and many others-- is distorting and misrepresenting what the original IAU draft resolution was about, in contradiction to what was said by those who were responsible for it, and is trashing their work.

"you wouldn't group the largest object in the vast swarm of objects beyond Neptune (the "Kuiper belt") with anything other than the Kuiper belt. The previous nine (or ten) "planets" encompassed the group of giant planets and the group of terrestrial planets and then awkwardly ventured out into the Kuiper belt to take in one or two of the largest of those objects. Using the word in this way makes no scientific sense whatsoever."

So according to Brown the specialists who made the proposal after working 2 years on it make no scientific sense. This is Michael Brown's obvious emotional nonsense and not Science. It is ok to be emotional, but it is preposterous that people give credit to what he says and trash the scientific integrity of the members of the Planet Definition Committee, as he is doing.

politics... not science.

>Let's not forget that Pluto is quite a bit smaller than our own little Moon.  Or just count how many moons of Jupiter alone are already bigger than Pluto.
>Then, is such *injustice* being done by putting Pluto in the "dwarf planet" category?
>It is only truthful to physical reality.

I am not arguing any of this. I said (please read my first post again) that I liked the original proposal very mych, and that the present proposal is worthless, not because Pluto was demoted, but because it leaves the definition of the word "planet" uncertain and ambiguous, while loosing the cultural and scientifc opportunities offered by the original draft.

I liked the original draft not because Pluto was considered a "planet" in it but because it was a radically new classification that I called "revolutionary". The usual classification ("planets" vs "minor planets") has resulted in the absurd practice of astrologers of taking Pluto into account but ignoring others like it, simply because they are called "minor planets" while Pluto --which should have been classified as a minor planet long ago-- is arbitrarily considered a "major" planet.

The members of the Committee knew well what they were doing. The proposed "Plutons" are a class based on origin, composition, size and other physical characteristics rather than just dynamics as had been so far. It is a a new classification thought to be simpler and more useful and realistic from the scientific point of view which has resulted from the evidence accumulated over the years.

It is a pity that the scientific and professional integrity of the members of the
 Planet Definition Committee, as well as the scientific and sociological merits
 of their proposal is being trashed so gratuitously in the name of science.

If the proposition had been approved we would have had a better, more realistic and scientifically responsible classification that pays tribute to the differences and the similarities between individual planets, without the hegemony of size and absurd notion of astrologers and popular culture that "small" means "insignificant" or "class B celebrity", a notion that Pluto pulverizes.

It is everybody's prerrogative to think that I or the scientists of the Planet Definition Comitee are wrong and that Michael Brown is rigth, because he is... well... Michael Brown. The politics and emotionalism of this is evident.



Date: Sun, 27 Aug 2006 08:24:18 -0600
Subject: Re: [Centaurs] the IAU resolution -- politics, not science, 3

>If this is still too ambiguous, than what other criterion you would have added to make the definition of 'planet' even more rigid and 'certain'?

according to the resolution, Pluto is a "dwarf planet", but a dwarf planet is not a planet... this is hilarious!



Date: Sat, 03 Feb 2007 20:05:27 -0600
Subject: [Centaurs] Pluto, perception and planetary politics

Pluto, perception and planetary politics
by David Jewitt and Jane X. Luu
(Winter, 2007 issue of 'Daedalus')

"calling Pluto a planet was un unhelpful and ultimately unjustifiable matter of
 public relations and planetary politics, not science."

"do scientists really make progress democratically, by voting...?"