Neighborhood clearing... That´s laughable, to say the least. There seems to be no end to the arbitrarieties they can introduce to the definition. I make Owen Gingerich´s words mine.

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Why fix what? What is NH's problem with this? Instead of visiting the last remaining planet, looking like a compulsory excercise to complete the list, now it is really a new horizon. The first spacecraft dedicated to the Kuiper belt, the first closeup look at a KBO! Those objects astronomers of today are trying very hard to get tiniest bits of information from with enormous efforts, and this thing is actually going there!
So do I. And from Charon please!

Well, I'm disappointed. I'm disappointed in the IAU's decision, yes, but what I'm mostly disappointed in is seeing a group of mostly otherwise reasonable people treating this like it's some sort of huge victory, or that they've somehow been personally vindicated by this.

This is not a case of 'Science over Popular Opinion'. This is a case of Elite Opinion over Popular Opinion. There's no science in "Them thar thins be movin' funny." I'm not going to go so far as Doodler and suggest that this was some sort of vendetta, but I do think this had nothing to do with logic, and everything to do with emotion.

And this is definitely not a case of 'Logic over...' well, anything, really. As far as I can tell, by this definition, Earth has only been footnoted in as a planet. There's no way anyone could reasonably consider the Moon to be small enough to be discounted in the "orbital clearing" definition. Earth's orbit is heavily disturbed by the Earth, to the point where I can't accept it as being a dominant body, or having cleared its orbit. There's no logic in footnotes of convenience.

It's clear to me that this issue isn't over, so we can all stop patting ourselves on the back, or patting the IAU on its back, and just wait for this to start up again. Nothing has been accomplished here, except garnering the ire of those who disagree with the IAU. The popular opinion of an elite few now has to withstand the beating of the popular opinion of everyone else. I'm going to wait and see if the IAU's made of stand or bedrock.

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You can't take the sky from me.

And Titan is currently the most oddball satellite, being the only satellite in the solar system with a thick atmosphere.

Ganymede is an oddball because it is the only satellite with a known magnetosphere.

etc. etc.

I agree about the footnote. I can understand Jupiter and Saturn's satellites being considered clear since the planets are a much larger size and the accretion theories suggest the moons formed in orbit around those large planets. However, the Giant Impact Hypothesis would suggest that the moon did not form around Earth because of Earth's immense gravity but that it formes elsewhere. Perhaps it was a co-orbital twin called Theia, which the Earth attempted to clear but ended up colliding with. The Moon would, thus, represent a failed clearing attempt instead of a successful clearing event. The result is a Moon, or satellite planet, massing over 70 exatons (1.3%).

Neptune also has a large moon, Triton, which was also not formed in situ. Current theory suggests that the satellite was formerly a planet, or an uncleared object. Since Neptune will destroy and consume Triton in a short about of time (astronomically speaking), it's more precise to say that Neptune is still in the act of clearing it's orbit, but has not finished. Unlike arguments of "safe" resonances, the consumption of Triton is a relatively dynamic event and shows that the IAU definition is self-contradicting.

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"What you think you thought you saw you did not see." Agent J, MiB - Manhatten Bureau

It would be simpler to describe the Earth-Moon system as a double planet. It's not as if the Moon doesn't orbit the Sun directly anyway.

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What's laughable? Frankly, I have read this forum for days and I can't find a scientific reason from those who are against the IAU resolution. It seems that many here are unable to see why the Kuiper and the asteroid belts are called "belts".

Ara Pacis, Triton is orbiting Neptune, which means that the gravitational influence of the latter makes Triton a satellite and not a wandering "dwarf planet", thus Neptune has cleared Titon from its own orbit.

Yes, there are many KBOs near Neptune's orbit, but that doesn´t mean it "hasn´t cleared its orbit", since these bodies, including Pluto, are in some kind of orbital resonance with neptune.

But please, don´t mention trojan asteroids anymore, since , as it's been said so many times before, the mass of all these asteroids is inferior in many orders of magnitude to Jupiter's or Neptune´s mass.

The IAU resolution is not perfect: no decision on this subject will ever be perfect, buy it's the best I can imagine, especially compared to the strange alternatives I've read on this forum.

What ridiculous arguments to make!

I find it amazing that Alan Stern & Owen Gingerich - both astronomers, and members of the IAU, who are opposed to the resolution in fact adopted, can complain about the end result of the process when they did not even bother to hang around and participate in the final debating session and subsequent vote over the definition!

Any complaints they may have with the decision are simply sour grapes and completely without foundation! They knew full well of the process that was being followed, and their non-attendance indicated staggering hubris, and its hard to believe they can't realise and accept that their non-attendance meant they forfeited their ability to legitimately criticise the decision arrived at. If defining a planet was really as important as they seem to be making out - why on Earth were they not able to hang around for a few days to participate in the final deliberations?

For Owen Gingerich in particular, its hard to believe he has any complaints - given he was there in Prague a few days prior helping to try and come up with a definition, and then he left!

BBC Article from Sticks

Alan Stern's complaint here is simply staggering in its ignorance. For someone of this education, what he says bears little resemblance to reality. Has Mr. Stern ever heard of the Electoral College that convenes after each Presidential Election in the US to vote upon who will assume the Presidency? Is he aware that if a member of this Electoral College fails to turn up, they can not cast their vote down the wires and expect it to be counted?

In fact, after the election of 2000, the results were so close in the Electoral College - 271-267 (IIRC), if only a handful of people had have decided they didn't need to turn up (far less than the number of astronomers who apparently decided they had more important things to attend to - in real terms and % terms), then in fact Al Gore would have been elected President 6 years ago and (this is for you 777 Geek) - An Inconvenient Truth would never have seen the light of day!

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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident." Arthur Schopenhauer - renowned 19th Century German philosopher.

You've posted this same paragraph in another thread. Since Stern is not talking about the electoral college, I'm not sure how you can claim that he is ignorant of it, much less staggeringly ignorant.

Perhaps, then, you can easily explain (using numberic specifications and real data) why they are belts.

It seems to me that once to start trying to put numbers on how wide the "orbit cleared" zone must be, and on what % mass needs to be cleared, that you start to have problems fitting Earth in and excluding (for example) Ceres.

This kinda looks to me like the infamous pornography definition: "I'll know it when I see it."

Or an elephant?

There are lots of things that we know when we see them, but the boundaries are indistinct. Take the colour blue for example. We all know the colour blue when we see it, but the actual boundary with green is indistinct, which is why you occasionally get people arguing whether a particular item is blue or green.

I'm sure the astronomers who voted for the criteria 'cleared the neighbourhood of its orbit' will know an example when they see it - which is why they were so adamant that Mercury, Venus.....Neptune had done so and Pluto hadn't. But they didn't really have much time to think of a more formal definition. I expect this bit of the planet definition will be firmed up in the near future. (The astronomers who opposed the definition didn't principally do so because this criteria was unclear, but they disagreed as to whether it should be a criteria at all.)

As a planet would clear its neighbourhood through its gravitational influence, what will be ignored is any object in those few circumstances where a planet's gravity cannot clear it (no matter how big the planet is). This includes any object in orbit around the planet; any object in the Trojan points, and any object in a synchronous orbit.

But there will be boundary issues as with any definition of this nature. They'll deal with them as and when they get an actual physical example. (There's no point doing so beforehand, as there may be some unknown physical process at work that means this particular boundary will never be an issue.)

Provided those absent were from the Bush states. P.S. That's about as political as you can get for us Americans.

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Why are they belts? I think it's so obvious that it didn't need any explanation. You can start looking in Wikipedia and then move to any other books on the Solar System.

You can find thousands of asteroids in Earth's orbital zone but first, their mass is only a tiny fraction of Earth's, and second, their origin and composition are unrelated to Earth's, unlike the asteroid belt, where most bodies, including Ceres, share a common origin. Finally, like in Neptune's case, Earth has gravitational domination over its zone, unlike Ceres or Pluto.

What bothers me is, what if there simply didn't happen to be a Neptune? Would that have made Pluto a planet suddenly?

Looks like you're correct. But if I understood correctly the pre-voting discussion, it was meant to include only the trans-Neptunian dwarf planets.

Resolutions 6A and 6B were created to give Pluto a special status as the first of its kind as some sort of consolation for people who didn't want Pluto to get demoted.

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Pluto doesn't dominate its neighborhood, with or without Neptune because Pluto is just another Kuiper belt object. In fact, Ceres probably has more dominance in asteroid belt than Pluto in Kuiper belt. After all, Ceres has significant fraction of all asteroid belt's mass in it, Pluto is far smaller compared to the Kuiper belt.

If Neptune and other KBOs suddenly disappeared, situation might be different...

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If it never happened to be a Neptune Pluto would not have been discovered when it was and the way it was, since it was a matter of chance when looking for the responsible of faux anomalies in the orbit of Neptune. No Neptune, no anomalies (real or miscalculated), no discovery of Pluto.

The order of the discoveries of KBOs would possibly be a different one from the one in our History, another KBO would have been discovered first and been termed "the 8th planet" (No Neptune so it would be 8th and not 9th), and now it would be demoted.

Another possibility is that there not being a Neptune, and thus no early discovery of Pluto, the discoveries of KBOs would have been severely delayed.

Maybe no KBO would have been discovered at all by now, so the IAU meeting would not have taken place.

I thought the meeting was a regularly scheduled affair? Did you mean, maybe the vote wouldn't have taken place?

The concept of clear is, itself, not clear. The past tense, "used", suggests a static present, and the action of Neptune and Triton belies this. It's a minor nitpick, but the larger issues of claiming clear = resonance are still unresolved. I think there are many scientific arguments against the current theory. Of course, scarcity in direct assaults on it are probably due to the lack of specificity in the definition. In other words, the new definition is hiding in ambiguity and claims the classic eight by fiat, not by examination.

It comes down to the science of communications and taxonomy, as both the first proposal and the adopted proposals have science to support them. I still think location is a second (or lower) order classification level for objects. A Hydrostatic Equilibrium is just as scientific and provides a brighter line. HE may be fuzzy, but objects are either above or below that physical and empirically derived limit. "Clearing a neighborhood" is currently undefined, but most unofficial arguments suggest orbital or mass dominance criteria for it. The definition of clear will probably end up being a mish-mash of several criteria, some of which may even be contradictory.

Contrary to what some have suggested, "clearing the neighborhood" is not just about mass and gravity. Tidal effects are related to spin. Time between encounters is dependent upon period. Gravitational slingshot is related to orbital speed. When an object is in a slower orbit it has less speed to imbue upon a passing object which would cause it to "clear the neighborhood". In other words, "clearing the neighborhood" is not something a planet does, it's an act the sun performs using one object upon another. If an object's gravity was the only determinant for "clearing the neighborhood" then accretion would be the only logical result, since ejection relies upon more mechanisms and forces than an object's gravity.

Again we come to my primary disagreement, which is that orbital elements define systems and are, therefore, systemic properties, not inherent properties, and I think a definition of a planet should be inherent. A planet should be defined by what it is instead of where it is.

Those people who want to argue about what a belt is should look at one. The Kuiper Belt is 2/3 the radial width of the entire up-wind solar system (30AU v. 20AU), and contains almost twice as much planar area (8,873sqAU v. 15,775sqAU). The Kuiper belt is a belt in the same sense that a boilersuit is a belt because it goes around the body. These are not narrow bands but vast regions. Discarding some objects because they exist in these regions of non-empty space makes little sense when you realize the 4 inner "planets" occupy a region with the same radial width as the "asteroid belt" (about 1.2AU for both). However, they have not been discarded because one has not cleared out the other three, outmassed the other three, or cast the other three into resonances. I would say the IAU resolution is inconsistent, except that they have not yet defined what consistency is.

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I posted a bit about this in the other Pluto thread, so I'm not going to unintentionally hijack two of them because that would be rude. Anyone can read my more detailed thoughts there, should they care.

However, I thought it worth mentioning again that the definition does not choose dynamical properties instead of physical; it is based on both. This is how good science is done: by using all the info you've got, not cherry-picking. The definition is not based on 'where' it is, it's based on what it is, what it's doing, and how it got there. That's "and", not "or".

I agree that the way it's laid out is needlessly wishy-washy though. Perhaps it's implicit to most of the planetary astronomers who know what they're looking for, but it apparently looks a fudge to everyone else. We can only hope they revise and improve it in future.

That makes about as much sense as classifying electrons by how many other electrons are in its orbital. Aparently, hydrogen is the only element with electrical properties... every other element has a cloud of small negative system particles.

I prefer labelling them all as particles, subclassed into baryons and leptons, and further subclassed into neutrons and protons, etc...

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"What you think you thought you saw you did not see." Agent J, MiB - Manhatten Bureau

You are right, I meant the vote. But come to think of it, unless the meeting was scheduled 160 years in anticipation, we cannot say that in the Neptuneless Universe everything would have worked the same.

The main consecuence of there not being a Neptune would be no "clearing of the orbital neighbourhood" (nice wording, I am beginning to like it ) of Neptune

So I think the Kuiper Belt could be nearer to us. Also there would have been a different history for every object in it, specially for the ones which in our "real universe" are resonant with our Neptune. That includes Pluto.

So the answer for Ken G is "if there never was a Neptune, then there never would have been a Pluto". At least not the Pluto we know.

Would there be an IAU? I wonder

Meaningless analogies aside, the IAU disagrees with you. Since they're the ones who've spent their lives studying this stuff and understand what's going on "up there" better than the rest of us, I'm kinda inclined to go with them, not the public vote.

If you want to agree to disagree, and side with the IAU proposal, that is one thing; but don't try to argue against me using an Appeal to Authority Fallacy.

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Remember that most of the "ones who've spent their lives studying this stuff and understand what's going on "up there" better than the rest of us," were'nt there when this thing got voted in.

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Duly noted, and I will happily agree to disagree; I'm not here to start an argument, I'm just putting the other viewpoint across. But please don't try to argue with me by making meaningless comparisons designed to ridicule a sensible POV. My reply was equal to yours.

This all turning very dark now, which I don't like one bit. I'm a nice guy, really. Quits?

jt-3d:Most of the ones who felt strongly enough about it were there to vote. It's not as if there was a secret conspiracy to keep anyone away.

I don't think my use of analogy was a fallacy. Analogy is always suspect, but the concept of objects in orbits not being defined by how many are in the orbit is maintained. If you want something more astronomy related then look at stars: they are stars, no matter how many are orbiting one another or in a cluster. Galaxies are called galaxies no matter how many are in a cluster. Feel free to show me counter examples.

Also, the issue of people voting because they have strong feelings is not good logic. The concept of he who is loudest is rightest may work in politics, but it is bad science. Surely, there are more empirical data to support the resolution... the IAU just hasn't presented it yet.

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Greaaaaat.....next thing you know, they'll be talking about the dwarf planet Gimli, which is gravitationally bound to a much larger, better looking "elf" planet (one that mostly dominates its orbit) named Galadriel. ^_^

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Quantumfoamy.com, my astronomy/astrophotography blog.

Yes, I agree it's impossible to come up with a "perfect" and "scientific" definition of "clearing the neighbourhood". But the bottom line is clear: Pluto is not a planet (a large one, at least, ) because it's a member of a population of similar bodies called the Kuiper Belt, which, in addition, are influenced by Neptune's gravity.

Hydrostatic equilibrium is more scientific? well, we have to bear in mind that hydrostatic equilibrium (roundness) depends on composition, internal temperature and collision history. Therefore, as a scientific criterion it's far from perfect. Mimas is round with a diameter of 397 km and a mass of 3.752x10^19 kg, but neither Pallas or Vesta, with a mass of more than 2.2x10^20 kg (and with a mean diameter larger than 500 km) are round. Wher do we drae the line? Again, we should use arbitrary criteria, but having fifty planets instead of eight.



But the fact is that where is important!. Distance from Sun influences composition, size and orbital characterisctics of a planet, therefore it's IMPORTANT.