Demote The IAU!!!!

jordanch68 · Aug 25, 2006

What I want to know is how did this decision get left up to the only geeks in the world who haven't watched Star Trek? http://en.wikipedia.org/wiki/Star_Trek_planet_classifications All I ever needed to know about planets I learned from Star Trek <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

serak_the_preparer · Aug 25, 2006

It might be that there is no definition of 'cleared the neighbourhood around its orbit' that is valid, in which case the definition of planet is internally self-contradictory and the IAU will have to go back to the drawing board! Good point. It may be that the IAU will find itself revisiting this definition some years down the road. There were romantics on both sides of this debate. Romantics who want the label 'planet' to mean something, to confer an honor and rank of some kind. Romantics who are attached to Pluto having been the 9th planet for long enough that it should remain the 9th planet. Why not get around the argument entirely by noting that Pluto-Charon orbit a common center of gravity, and therefore is a double planet? The mass of the double planet together should please the crowd that wants planet status to be something special which is earned. And the retention of planet status would please those who want Pluto to remain on the roster. Realistic solution for a romantic argument? [Edited to include 'remote' in subject.]

MeteorWayne · Aug 25, 2006

You mean astronomy scientists? Maybe people who learned everything they know from Star Trek are the geeks? <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

docm · Aug 25, 2006

OK....who runs the crack concession at the IAU conferences? Methinks it was augmented <img src="/images/icons/tongue.gif" /> <div class="Discussion_UserSignature"> </div>

serak_the_preparer · Aug 26, 2006

OK....who runs the crack concession at the IAU conferences? Actually, it was quite a nice, clean little crystal meth lab. Run by a respected Czech chemist. You may wish to have a look at Astronomers Behaving Badly (actual title 'On to Rio!') by Steve Maran. Where you'll find this paragraph: Less than a third of IAU’s members actually came to Prague -just 2500 give or take- and by the end of the meeting when the Pluto decisions were taken, only a fraction of those were present and voting. By all accounts, a tough gang of solar system experts prevailed to dump Pluto from the planetary ranks. But, as the media report, other astronomers say that they have just begun to fight. The author adds: 'So when the IAU next meets, in Rio in August 2009, I will be there. Ready to wheel and deal and to vote.' Methinks it was augmented <img src="/images/icons/tongue.gif" /> Word on the ulicka is Jindøich Šilhán showed up with some Pervitin and the place went crazy. But that rumor is unconfirmed (my guess is it was Jiøí Dušek, a known party animal).

vidar · Aug 26, 2006

Calling that object ’Death’ backfired http://en.wikipedia.org/wiki/Pluto_%28mythology%29 . It’s dead as a planet, it always was and always will be.

jaxtraw · Aug 26, 2006

I think this was an incredibly silly decision. It wasn't a scientific definition, it was engineered entirely to include 8 very dissimilar objects and exclude some others, for the entirely arbitrary reason that people want an exclusive club called "The planets" which has only those 8 members. On what scientific basis should "planets" be few in number? Planet should be a generic term, like "animal", which then has subcategories e.g. gas giant, terrestrial, icy and so on. Jupiter and Mercury are as dissimilar as can be in every respect, other than they're both bright objects from Earth that ancient astronomers/astrologers noted. It's like trying to define a special class of life form called "important animals" and then desperately tinkering with the definition so it includes lions and elephants and excludes hyenas and tigers. What's particularly sad is that we're in an exciting phase of starting to learn about other solar systems- the IAU has responded with a pettiflogging reclassification which is utterly parochial.

Saiph · Aug 26, 2006

except animal isn't a generic term, it's just a very broad one. Pluto has far more in common with KBO's than with the other planets. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

jaxtraw · Aug 26, 2006

Planet needs to remain very broad. It's not sensible to make it a narrow definition- that should be the job of subcategories, just as "white dwarf", "neutron star" and "red giant", very dissimilar objects, are all "stars". Planet should be used, as most people would naturally use it, for anything "world-like"; if it walks like a planet and quacks like a planet, it's a planet. The mistake the IAU have made is implicit in their terminology- saying "planet" and "dwarf planet" are different things, rather than dwarf planet being a more narrow category of planet, which its name correctly implies. I think TBH that's how most people will use it anyway- "it's a planet, dwarf type". Jupiter and Mercury have nothing whatsoever in common other than they're both in near-circular orbits, and yet they both get to be planets. The near circularity of their orbits can hardly be a defining characteristic- if Jupiter were in an eccentric, elliptical orbit, would we say it's not a planet? And what of the extrasolar giants in such orbits? Pluto and Mercury at least have in common that they're solid. The frequent use of the word "demotion" is deeply worrying in all this- it reveals the implicit idea that if something isn't a "planet" it's inferior, unworthy. I'm sure I read that there were objections to New Horizons because "Pluto isn't a planet really" which is a bizarre way to consider scientific priorities. Two of the most interesting places in the solar system currently- Europa and Enceladus- aren't planets, and if we were being all sniffy about categories we'd probably call Enceladus a Dwarf Moon and ignore it. In which case we'd have missed some fascinating and important science.

Saiph · Aug 26, 2006

First, Neutron Stars and White Dwarfs aren't stars, they're Compact Objects. This falls into the same problem (one I agree with) of having part of the term be in the name that's misleading. A neutron star isn't a star...and a dwarf planet isn't a planet. So, why include the term?! Anyway, the problem with pluto is it doesn't resemble the other planets. It's orbit is littered with similar sized objects, it's density and composition are very dissimilar as well. The only thing it really shares with other planets is a round shape. So, why do Mercury and Jupiter both get the planet title? That's a fair question, as they are both more precisely classified as a terrestrial planet and a jovian planet. I wouldn't care if pluto was just put into a smaller subcategory...but the thing is it doesn't control it's region of space like all other planets do (regardless of type). I will agree with you on the term "demotion". I don't like it either, as there really is no heirarchy. It's been reclassified, that's it. And as for not sending things to pluto cause it isn't a planet...anybody who says that is missing the point, as you indicate. Oh, and no article I've seen has reported Pluto's eccentric orbit being an official factor in this decision. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

vidar · Aug 27, 2006

Its hard to see how the term dwarf planet fits the real world because there are so few of them. But if we exclude the fourth restriction for a while, “Is not a satellite of a planet, or other nonstellar body”, it would be interesting to know if some of the following objects could be categorized as dwarf planets. http://www.solarviews.com/browse/misc/plntmoon.jpg Personally, I don’t mind double planet systems.

jaxtraw · Aug 27, 2006

Please list- 1) The other bodies (other than Pluto's satellites) which share Pluto's orbit. 2) The similarities in density and composition shared by Jupiter and Mercury.

alokmohan · Aug 27, 2006

What you think of mercury?

vidar · Aug 27, 2006

What you think of mercury? ----------------- Mercury looks very much like Jupiter’s ‘moons’ Ganymede and Callisto. Mercury has even a big scar and an oval orbit. http://upload.wikimedia.org/wikipedia/en/thumb/8/88/Reprocessed_Mariner_10_image_of_Mercury.jpg/300px-Reprocessed_Mariner_10_image_of_Mercury.jpg Mercury might not be in its original orbit, and can have been knocked out from somewhere else. Mercury has certainly not ‘cleared its own neighbourhood’, at least not without a considerable help from its neighbour, the sun.

MeteorWayne · Aug 27, 2006

1) The other bodies (other than Pluto's satellites) which share Pluto's orbit. That's a big list. And it increases almost every day. I'll try and put one together, but it will take a while, and be obsolete before it's done. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

jaxtraw · Aug 27, 2006

Don't you actually mean that there are many objects in a very very large region of space called The Kuiper Belt? That's quite different to sharing an orbit.

MeteorWayne · Aug 27, 2006

Well, there are a few plutinos. And the defination was IIRC to dominate it's orbit. See this link All the white dots are Plutinos, in 2:3 resonance with Neptune, the same orbital type as Pluto. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

MeteorWayne · Aug 27, 2006

Since the intro goes by very fast, I'll copy it here This is from the Minor Planet Center The Outer Solar System This animation shows the motions of objects in the outer solar system, beyond the orbit of Jupiter, over a 100-year period at 200-day intervals. The orbits and current locations of the Jovian planets (Jupiter, Saturn, Uranus and Neptune) are shown. The current location of Pluto is indicated by the large white crossed circle. High-eccentricity objects are shown with cyan triangles, Centaurs as orange triangles, Plutinos as white circles, "Classical" TNOs as red circles and Scattered-Disk Objects as magenta circles. NOTE: The strange behavior exhibited by the comets (a general heading inwards prior to the mid 1990s and a general heading outwards post 2000) is a consequence of plotting only those comets currently observable (as of mid 2002). Around this date, all of the long-period comets would have been at or near perihelion. Fifty years either side of this date they are all far from the sun. If the full cometary catalogue had been plotted, this effect would not be so noticeable as there would be inbound and outbound comets visible on each pre-2002 frame. Here's the full animations page. Lots of fun stuff to look at, and relevant to this discussion. animation page link <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

jaxtraw · Aug 27, 2006

I'm arguing that the definition "dominate its orbit" is fuzzy and arbitrary, and I think it's not unreasonable to conclude it was put in specifically to exclude our small icy worlds, because the outer solar system is the realm of eccentric orbits and is relatively densely populated with these little worlds. It's much like some political body trying to define what a "people" is, and deciding that a people must control their territory, thus allowing the English in but excluding, say, the Sioux, Kurds or Inuit, because they are minorities within a more broadly defined territory. The English might approve of that definition; the Sioux, Kurds or Inuit less so. I'm really getting at the question of what justifies this criterion from first principles. That doesn't even address the problem that we now have a special category called "dwarf" that has no definition contingent on smallness. It's entirely possible (if unlikely) that we could end up with a "dwarf" larger than a "real" planet!

MeteorWayne · Aug 27, 2006

Were you able to look at the animation? Do you see how many plutinos there are? At least a few dozen. And that was 4 years ago in 2002. We probably know of twice as many today. The fact is Pluto is not unique in orbit or composition or size in it's orbital range. How many Neptunes are there? Even, how many Mercurys? BTW, I agree with you that dwarf is a poor choice. I preferred the old Minor Planet. As in the IAU's Minor Planet Center <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

jaxtraw · Aug 27, 2006

Why does it matter how many there are? Why do you think the planet category should be limited to less than 10 members? Why is there a presumption of exclusivity?

vidar · Aug 27, 2006

Interesting animations MeteorWayne. Do you know what the mass of the objects in Jupiter’s orbit is? It would be interesting to know what Jupiter’s mass would be if it managed to ‘cleared its own neighbourhood’. Would it be enough to ignite Jupiter?

MeteorWayne · Aug 27, 2006

They are all quite small. Asteroids and comets, none of the asteroids in the class of Ceres. All the asteroids and comets in the asteroid belt, Kuiper belt, Oort cloud,and everywher else TOTAL less that mercury's mass IIRC. I'll have to check for a refernce to show that what I recall is correct. MW <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

Saiph · Aug 27, 2006

Jaxtraw: There are plenty of other KBO objects of similar mass in the vicinity of Pluto. Even if they aren't right next to it, they are far closer in size, and orbit than for any other planet. If one points out Jupiter's trojan asteroids, I'll counter with the fact that Jupiter's gravitational influence has corraled them into the trojan points. Also, the "orbital dominance" isn't as arbitrary and ill-defined as you'd think. As for comparing Jupiter and Mercury. Sure, they're different, but they are both planets. Ones Terrestrial, the other is Jovian, as subclasses. However, they do share some traits that make them planets, not moons, asteroids, brown dwarfs, etc. Pluto doesn't really share all of those traits. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

MeteorWayne · Aug 27, 2006

Saiph, The actual IAU resolution doesn't define it at all, leaving it open to anyone's interpretaion. It makes no reference to any other supporting or clarifying information. That scares even me, and I'm an 8 planet guy! Do you have any knowledge of where such clarification might be? Cleared is much different than, "orbital dominance" That link is to a Wikpedia article and orbital dominance is not referred to in the resolution. Here is the actual resolution from the IAU page. RESOLUTION 5A The IAU therefore resolves that "planets" and other bodies in our Solar System be defined into three distinct categories in the following way: (1) A "planet"1 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. {italics mine} (2) A "dwarf 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) shape2 , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. (3) All other objects3 except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies". --------- 1The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. 2An IAU process will be established to assign borderline objects into either dwarf planet and other categories. 3These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.--------- IAU Resolution: Pluto RESOLUTION 6A The IAU further resolves: Pluto is a "dwarf planet" by the above definition and is recognized as the prot <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

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