“Honk if Pluto is still a planet”

In the last update to my post yesterday noting the demotion of Pluto to dwarf planet status by the IAU, I mentioned this short BBC article and the comments of Dr Alan Stern, who leads NASA’a New Horizons mission to Pluto, saying that like-minded astronomers would try to get Pluto reinstated. He has more to say here, but there are more serious reservations on the vote from Dr Owen Gingerich who chaired the IAU’s planet definition committee, which spent two years producing an earlier, rejected, draft definition More on the controversy And via John O’Shea. The photoshoppers are on the case.. hehOwen Gingerich’s comments in the BBC article

“In our initial proposal we took the definition of a planet that the planetary geologists would like. The dynamicists felt terribly insulted that we had not consulted with them to get their views. Somehow, there were enough of them to raise a big hue and cry,” Professor Gingerich said.

“Their revolt raised enough of a fuss to destroy the scientific integrity and subtlety of the [earlier] resolution.”

He added: “There were 2,700 astronomers in Prague during that 10-day period. But only 10% of them voted this afternoon. Those who disagreed and were determined to block the other resolution showed up in larger numbers than those who felt ‘oh well, this is just one of those things the IAU is working on’.”

Professor Gingerich, who had to return home to the US and therefore could not vote himself, said he would like to see electronic ballots introduced in future.

And those like-minded astronomers?

Stern said like-minded astronomers had begun a petition to get Pluto reinstated. Car bumper stickers compelling motorists to “Honk if Pluto is still a planet” have gone on sale over the internet and e-mails circulating about the decision have been describing the IAU as the “Irrelevant Astronomical Union”.

Btw you can buy one of those bumper stickers here

Meanwhile seven well-known dwarfs have offered Pluto a new position..

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  • Occasional Commentator

    I see no reason to think the result would have been any different if the turnout was higher. Owen Gingerich just sounds like a sore loser.

  • Pete Baker

    He also seems to have understated the number who voted, the article I noted in the update gives a figure of 424.

    But he may have a point on the decision being taken by such a small group, in relation to the number of professional astronomers.

  • dodrade

    Does this mean that Pluto will soon be removed from Disney World?

    Being serious, we must ask ourselves, if Pluto had been discovered yesterday, would we make it a planet? The fact that there has been no great enthuasism to make Xena the 10th planet despite it being bigger than Pluto suggests otherwise. The save planet pluto campaign seems based on sentiment rather than science.

  • Pete Baker


    Did you miss this link? 😉

    On your serious question, probably not. But I get the feeling the manner in which the discussion took place, and the decision was made – not to mention the focus placed on them – caught a lot of those involved by surprise.

  • ben

    Gingerich had no problem with the process until his absurd proposal was shot down.

    Does he think that there’s some sort of scientific process about his grumping and whining and ad hominem attacks and appeals to evidence-free populism? I’ve seen the paper that backs up the successful proposal and the evidence is absolutely overwhelming — there are many significant characteristics which the eight planets have and that Pluto simply does not share. There are many significant characterstics that “Xena”, Ceres, and untold other objects have that Pluto *does* share. It’s that simple. There are numbers and tables and charts that are a lot more convincing than a “honk if you think what you were taught in school should be considered incontrovertible fact forever”.

  • Pete Baker


    While I’ve stated here in previous posts that Pluto shouldn’t be regarded as a planet, there are some valid points to be made against the definition as adopted.

    Unless I’m missing something, the characteristics you mention, which the eight planets share – and those which Pluto Xena, Ceres et (unknown) al share – do not appear to be part of the definition of a planet, or in the dwarf planet definition.

    “(1) A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.”

    There’s also the point, as some astronomers have indicated, there are few, if any, of the planets that could claim to have completely “cleared the neighbourhood” around their orbits.

    Additionally the exclusion of Charon from dwarf planet status – by the use of the clause “not a satellite” – seems arbitrary. Surely, if the distinction between planet and dwarf planet is to be adopted, it would be more consistent to include Charon as a dwarf planet and have Pluto/Charon as twin dwarfs?

  • Occasional Commentator

    The IAU did not rule out Charon, they simply didn’t explicitly rule it in as yet. They did rule out satellites from being dwarf planets, but the crucial point is that Charon is not a satellite by the IAU’s own definition. Therefore Pluto and Charon are each dwarf planets (or maybe I should say a single ‘dwarf planet pair’) by the IAU’s own definitions, based on my own unofficial attempt to interpret their rules. (There are many others that agree with me if the Wikipedia talk pages are anything to go by).

    The definition of satellite is based on the location of the ‘centre of mass’ of the pair of objects. In the case of Pluto and Charon this centre of mass isn’t within Pluto – therefore Charon is not a satellite. In the case of the Earth and the Moon for example, the centre of mass is within the earth – meaning the moon is a satellite of course.

    As for the ‘cleared the neighbourhood’, I’ve taken it to really mean ‘dominate the neighbourhood’. We know Pluto and Neptune share part of their orbit. If they were to meet Pluto would be flung off or crash into Neptune, while Neptune would continue on pretty much as before because it’s so much more massive. That’s why Neptune is the planet, and Pluto is the dwarf, even though Neptune hasn’t cleared Pluto from its path. See “clearing the neighbourhood” on Wikipedia.

  • Pete Baker


    The not ruled out/not ruled in aspect of the definition is what is at issue here.

    And there’s little point in the satellite reference other than to attempt to exclude Charon.. it shouldn’t be excluded btw.. but it was intended to be a concession to plutophiles – didn’t work.

    BTW The location of ‘centre of mass’ argument comes from the original, and rejected, definition of a planet – based entirely on gravity – which I’m begining to warm to.

    I wouldn’t place too much store in Wiki yet… it’s useful when scientific criteria have been established.. not so much when they are being contested.

    An example, in ref “clearing the neighbourhood”

    However, according to Dr Alan Stern, who leads the US space agency’s New Horizons mission to Pluto, Earth, Mars, Jupiter and Neptune have also not fully cleared their orbital zones either. Earth orbits with 10,000 near-Earth asteroids. Jupiter, meanwhile, is accompanied by 100,000 Trojan asteroids on its orbital path.

    “If Neptune had cleared its zone, Pluto wouldn’t be there,” he added.

  • abucs

    It all seems a little arbitrary.

    I wonder how fixed everything is ?

    For example, asteroids from the belt between Mars and Jupiter occassionally seem to be thrown around the solar system.

    I wonder if there is a certain arrangement of planets that will allow gravity to expel Pluto from the club or make it a moon of a larger planet.

    I read somewhere that planets can escape their solar systems and travel aimlessly in space, unwanted :o(

    I guess with the ‘former’ planets of our solar system being so stable for so long, as well as Pluto’s size (attraction to the sun) it might be impossible.

    Still, it would save all the arguements about Pluto’s planetary membership.

  • Brian Boru

    Pluto’s status as a planet became unsustainable when it became clear there are other bodies in the solar-system larger than it.

  • ciaran damery

    So Pluto doesn’t have the *gravitas* to be considered a ‘planet’. Is trua é sin. Yet some in occupied Ireland insist of refering to the territory as a ‘country’ or a ‘province’, even! An bfhuil siad ag magadh fuainn? Ar aon chumadh, slán Pluto.

  • Pete Baker


    “I wonder if there is a certain arrangement of planets that will allow gravity to expel Pluto from the club or make it a moon of a larger planet.”

    No. *shakes head*


    Pluto’s status had been in dispute for some time prior to the discovery of other celestial bodies larger than it – apart from the planets that is..

  • abucs

    i didn’t think so either Pete… just putting it out there.

    Smiles at you shaking your head.