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IAU Demotes Pluto to 'Dwarf Planet' Status 426

Posted by timothy
from the and-then-there-were-eight dept.
davidwr writes "It's official. Pluto's been demoted. It's now one of several 'dwarf planets.' I guess we can drop the 'Period' from 'Mary's violet eyes make John stay up nights.'" (Of course, no one says you have to privately agree with the International Astronomical Union.) Several readers have contributed links to the BBC's coverage of the downgrade, as well as the usefully illustrated story at MSNBC.
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IAU Demotes Pluto to 'Dwarf Planet' Status

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  • by SomeGuyFromCA (197979) on Thursday August 24, 2006 @10:39AM (#15969616) Journal
    many very educated men just screwed up nine planets...
    • Re: (Score:3, Funny)

      I agree! Not since Brontosaurus was renamed to Apatosaurus have I been this upset.
    • Re: (Score:2, Funny)

      by ajs (35943)
      The only mnemonic that I can ever manage to remember for the planets is:

      Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

      And, did anyone ever really think of Pluto as a planet?! At best, it's a comet that doesn't enter the inner solar system.
    • Re: (Score:2, Funny)

      This just in from Pluto...
      ...the IAU has been demoted to just a bunch of geeks with nothing better to do than reclassify frozen rocks.
      ...Earth astronomers destroy any chance of interplanetary relations with Uranus.
      ...Walt Disney may be rolling over in his grave, but Pluto discoverer Clyde Tombaugh is surely spinning!
      And... Congratulations IAU, thanks to you, anyone with born under the Astrological sign Scorpio now has no ruling planet.
      • by Rei (128717) on Thursday August 24, 2006 @11:12AM (#15969904) Homepage
        ...Walt Disney may be rolling over in his grave, but Pluto discoverer Clyde Tombaugh is surely spinning!

        At a rate of once every six days, nine hours, seventeen minutes, and thirty six seconds.
        • Re: (Score:3, Insightful)

          by Enrique1218 (603187)

          Clyde Tombaugh is surely spinning!

          In astronomy, they don't call it spinning, but "ro...tat...ing" (making finger quotes as I type). You have to give some respect to the man who discovered the biggest snowball that side of the asteroid belt

    • Re:my take on it: (Score:5, Informative)

      by Adhemar (679794) on Thursday August 24, 2006 @11:08AM (#15969856)

      I wouldn't call it a screw-up.

      The draft proposal was:

      A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet.

      Pluto would continue to be a planet, and Ceres, Charon and 2003 UB313 would become planets. However, this criterium is reached by hundreds, even thousands of other celestial bodies in our solar system. Under that proposal, all could gain planet status.

      The final text is:

      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.
      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) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
      Pluto is a dwarf planet by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.
      All other objects orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

      This definition does not define the terms "nearly round", nor "neighbourhood". But having a definition, rather than just an enumeration, is in my opinion a big leap forward. Demoting Pluto is a small price to pay.

      I quite like the additional criterion of dominance of a body in its neighbourhood. It's not as arbitrary as simply requiring a minimum mass or size.

      On the other hand, I do not like the fact that a planet should orbit to Sun to be called a planet. On this point, I preferred the original proposal in orbit around a star. I don't see why our solar system should be any different, why planet-like celestial bodies orbitting other stars are not called planets.

      • Re:my take on it: (Score:5, Interesting)

        by Rei (128717) on Thursday August 24, 2006 @11:15AM (#15969930) Homepage
        One thing that annoys me is that they added "is not a satellite" to specifically exclude Charon.

        Pluto orbits the sun, but it also orbits a point in space above its surface. Charon doesn't orbit Pluto, but orbits a point in space above the surface of Pluto, while it too orbits the sun. Can someone explain to me why this shouldn't be called a double?
        • Re: (Score:2, Informative)

          by GrayCalx (597428)
          I think they added that to specifically exclude all moons, not just Charon.
          • Re: (Score:3, Insightful)

            by jc42 (318812)
            Indeed, and the main other problem is our own moon. Various astronomers have commented that they consider Earth-Luna to be a pair of planets sharing a common orbit around the sun, and changing places periodically. (There are examples of this on a smaller scale in the Saturn system.)

            Not that it really matters all that much. As other astronomers have commented, they mostly just say "body" and give a list of specs. Terms like "planet" are a bit too vague to be useful as technical terms. After all, Mercury
          • Re: (Score:3, Insightful)

            by transami (202700)
            I think every other "moon" has an gravitational center within the parameters of the planet. Charon is the only case, so I agree Charon and Pluto should be considered "binary planets". It you want to call them 'dwarf planets' too b/c they're are relatively small, that's fine too. But they're still planets. And I will still think of them as such, as well as any other object orbiting a star.
            • I think every other "moon" has an gravitational center within the parameters of the planet. Charon is the only case, so I agree Charon and Pluto should be considered "binary planets".

              But isn't the Moon's distance from Earth slowly increasing thus, surely, the binary planet definition will also apply to the Earth+Moon eventually?
        • Re:my take on it: (Score:4, Interesting)

          by 2short (466733) on Thursday August 24, 2006 @12:04PM (#15970397)
          Not so. The original proposal (which had the "is not a satelite" clause) made Charon a planet.

          "is not a satellite" does not exclude Charon, because they picked a somewhat peculiar definition of "satelite" (barycenter of gravity inside the primary), which excludes almost everything we typically think of as a moon, but not Charon. This definition makes the Moon a satelite, but if the Earth had a slightly smaller radius but the same mass, the Moon would follow exactly the same orbital track, but suddenly be a planet.

          I beleive they picked this definition of "satellite" specifically to exclude Earths Moon. If you actually plot the orbital tracks of the Moon, Charon, and any other moons you like, one stands out like a sore thumb as the one that should obviously be said to be orbiting the Sun. It's not Charon.

          • Re: (Score:3, Interesting)

            by Rei (128717)
            Exactly what I was saying: the original proposal made Charon a planet, while this one excludes it, which I think is silly.

            They claimed to exclude Charon from being a dwarf planet, so they're obviously not using the barycenter definition to determine what a satellite is.
      • Re: (Score:2, Interesting)

        I agree that the change from orbiting a star to orbiting the Sun is peculiar. It also, to me, does not address the position of captured 'planet-like' objects such Titan or Ganymede which otherwise fulfil the requirements of 'planet' especially as they have also deleted the clause "and is neither a star nor a satellite of a planet" from the Planet definition (but left it in for Dwarf Planet).

        C+ - Very sloppy work
      • Re: (Score:2, Interesting)

        by banditski (163064)
        I agree that all planets - in our solar system or elsewhere - should have the same definition.

        Now about that definition - in my very naive view, shouldn't the definition of "planet" have something about the body in question orbiting in the plane of the star's equator? I think that would go a long way towards differentiating captured comets, asteroids, etc. from the "classically" formed planets.

        Can someone explain why that doesn't make sense?
      • Re: (Score:3, Informative)

        by Chysn (898420)
        > On the other hand, I do not like the fact that a planet should orbit to
        > Sun to be called a planet. On this point, I preferred the original
        > proposal in orbit around a star. I don't see why our solar system
        > should be any different, why planet-like celestial bodies orbitting
        > other stars are not called planets.

        Because they're only defining what a Solar planet is, not the general meaning of the word "planet":

        The IAU therefore resolves that planets
  • 8 Planets and 8 Dwarfs? Sounds simple enough...
  • by jameseyjamesey (949408) on Thursday August 24, 2006 @10:40AM (#15969618) Homepage
    My Very Eager Mother Just Served Us Nachos
    • Re: (Score:2, Funny)

      by legoburner (702695)
      not to mention all the planet posters that need updating... I am buying stock in black paint companies right now!!
  • by Lothar+0 (444996) on Thursday August 24, 2006 @10:40AM (#15969620) Homepage
    How will this affect Sailor Pluto [wikipedia.org]?
  • Astrologers panic! (Score:5, Insightful)

    by grub (11606) <slashdot@grub.net> on Thursday August 24, 2006 @10:41AM (#15969629) Homepage Journal

    So will this render all astrological predictions which took Pluto into account as invalid? I'm sure the kooks will come up with some excuse to explain how their previous charts were accurate at seeing the future as if they ~knew~ this all along.

    • by Rob T Firefly (844560) on Thursday August 24, 2006 @10:45AM (#15969662) Homepage Journal
      Astrologers will just keep on as before. The Astrological usage of the word "planet" includes the traditional planets as well as the Sun, the Moon, the planetoid 2060 Chiron, and really whatever else one desires to keep track of in their system of astrology.
      • Re: (Score:3, Informative)

        by smooth wombat (796938)
        NPR had an astrologer on last night and he said the same thing. Their definition of a planet is different than what the 'experts' say is a planet.

        Then again, when you're dealing with flimflam you can pretty much say whatever you want.

        The fact that NPR had this segment only served to legitimize this nonsense and continued to give hope to the gullible that astrology is valid.
  • A new one (Score:5, Funny)

    by suso (153703) * on Thursday August 24, 2006 @10:41AM (#15969633) Homepage Journal
    Much vodka easily makes John seek urination naturally
  • by HikingStick (878216) <z01riemer@noSPAM.hotmail.com> on Thursday August 24, 2006 @10:41AM (#15969637)
    I just can't understand why this story of Pluto's reclassification is deemed "breaking news" on the major news websites. It's not as if it just changed orbit and was streaking straight for New Jersey...

    Now that would be breaking news!
    • by Skye16 (685048) on Thursday August 24, 2006 @10:45AM (#15969663)
      And incredibly freaking awesome, even if it would be an extinction level event. I don't want to die or anything, but if I'm going to, a: I want it to be in a really huge explosion, and b: I want all of New Jersey to go first.
    • by jd (1658)
      It's more news that breaks. As in, breaks...
      • All existing school astronomy textbooks
      • All populat mnemonics for remembering the planets
      • Any sci-fi that refers to Pluto as a planet after the 21st century
      • All science museum exhibits showing the solar system
      • All astronomical software that allows you to view the planets

      I'm not sure hitting New Jersey would be good, though. Could you divert it so it hits Texas, or New Orleans?

  • by jo42 (227475) on Thursday August 24, 2006 @10:43AM (#15969643) Homepage
    Walt Disney is turning over in his grave...
  • by Frequency Domain (601421) on Thursday August 24, 2006 @10:44AM (#15969652)
    I learned "Mary Virginia eats many jam sandwiches under Ned's porch." Now it will have to be "...under Ned."
  • That's a good one. I started forgetting planet order right about the time I lost the name of every dinosaur. Funny how the mind works.

    I still remember a great one from when the USSR blew up. I think it was a contest in Games magazine or something. Anyway, it goes Gorbachev's khaki underwear always tends to ride up at long lines exiting boring Kremlin meetings. Compare with http://en.wikipedia.org/wiki/Republics_of_the_Sov i et_Union [wikipedia.org]. Amaze your friends! Fool your enemies!
  • by s-gen (890660) on Thursday August 24, 2006 @10:47AM (#15969685)
    Much-maligned Pluto doesn't make the grade under the new rules for a planet: "a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit." Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's.
    So how does Neptune qualify? Seems to me it too has failed to clear its orbit... of Pluto!
    • Re: (Score:3, Insightful)

      by unjedai (966274)
      If you consider that comets cross the orbits of all the planets, then none of the planets qualify.
    • Re: (Score:2, Funny)

      by Daetrin (576516)
      So how does Neptune qualify? Seems to me it too has failed to clear its orbit... of Pluto!

      Pluto's response to the breaking news: "Damn you Neptune! This is all your fault! If I don't get to be a planet then I'm taking you down with me!"

    • by shma (863063) on Thursday August 24, 2006 @11:09AM (#15969870)
      Actually, while Pluto comes closer to the Sun than Neptune, they are never that close. Pluto's erratic orbit ensures that it is well above the solar system equator when it does cross. The chart here [nasa.gov] shows how far it really is at the cross (chart is in AU =~ 149 billion meters).
    • by Vreejack (68778)
      I would assume that "clearing" does not include objects in resonance, which are actually held in position by the body in question. Pluto and Neptune are in resonance, as are any rocks that occupy Lagrange points. This rule seems to be directed against Ceres, which has so far failed to clear its orbit of a lot of other rocks (typically called asteroids).
    • by phlegmofdiscontent (459470) on Thursday August 24, 2006 @11:20AM (#15969967)
      "Clearing" basically means that all other bodies within an orbital range are much smaller. There are many asteroids that cross Earth's orbit, but none are larger than a few tens of km. All 8 planets have cleared their orbital zones. The remainder of objects in those oribtal zones are assorted junk (comets, Trojans, NEOs, Centaurs, Atens, etc). Pluto and Ceres do not qualify because there are objects of comparable size in their respective orbital zones.
    • Pluto's orbit is far more eccentric than Neptune's.
    • Re: (Score:3, Informative)

      If you added up the mass of Pluto and all the other similar objects that cross closer to the Sun than Neptune, you only get a tiny fraction of Neptune's mass. Neptune completely dominates the mass at that distance from the Sun.
  • by Anonymous Coward on Thursday August 24, 2006 @10:48AM (#15969702)
    I remember failing a second grade test because I missed pluto! Time I march down to the nursing home and give Mrs Johnson a piece of my mind!
    • I remember failing a second grade test because I missed pluto! Time I march down to the nursing home and give Mrs Johnson a piece of my mind!

      I got in similar trouble to telling my teacher that her solar system model was wrong because all of her planets were on the same plane. And, got in more trouble when I mentioned that Pluto is not the furthist planet from the sun, but rather Neptune was (at least, at that time). Of course, the worst was when I corrected a teacher whom said Saturn was the only plane

  • Stupid (Score:2, Insightful)

    by Otter (3800)
    As with the change of "brontosaurus" to "apatosaurus", this is completely foolish. Given the level of scientific illiteracy, what the hell is the point of taking something that everyone does know and declaring it to be wrong?

    Create the new definition with a stipulation that for historical reasons, Earth's generally accepted planets will remain in the planet class. There's nothing wrong with that. It's not like any meaningful astronomy research is going to get confused.

    • No kidding.

      Besides, if Pluto wasn't discovered by Clyde Tombaugh at Lowell Observatory in Arizona (US), I don't think there would have been much strong objection to demote Pluto as a dwarf one.

      Still it is a planet, I guess it's a compromise fro the pride.
    • by Billosaur (927319) *

      As with the change of "brontosaurus" to "apatosaurus", this is completely foolish. Given the level of scientific illiteracy, what the hell is the point of taking something that everyone does know and declaring it to be wrong?

      Ask the Creationists.

      To stay on topic, now that Pluto is no longer an "official" planet, Jupiter should be next. It's a brown dwarf star after all, isn't it? Even the definition of is a little up in the air [wikipedia.org].

    • Re:Stupid (Score:5, Insightful)

      by Reality Master 101 (179095) <RealityMaster101&gmail,com> on Thursday August 24, 2006 @11:21AM (#15969977) Homepage Journal

      Given the level of scientific illiteracy, what the hell is the point of taking something that everyone does know and declaring it to be wrong?

      "Everyone" knew there were eight planets prior to 1930. Did the world end when it was changed to nine, especially with something that wasn't even obviously a planet?

      Guess what? A whole generation of children will grow up with the new, consistent rules and won't know any different. What's unarguable is that the new rules are better. I'm all in favor of fixing things that are broken, even if certain curmudgeons are too mentally inflexible to make the adjustment. See also: the metric system in the US, which is kept down by the same curmudgeons.

    • by Intron (870560)
      Apatosaurus was first. Brontosaurus [wikipedia.org] was made up by someone at Yale who put unrelated fossil bones together, some from an apatosaurus, and claimed to have discovered a new dinosaur.

      Not sure why the IAU gets to decide what a planet is. There seems to be useful no scientific distinction between a planet and a planetoid. Popular meaning should prevail.
  • Actually, "dwarf planet" is considered rude.

    It prefers to be called a "little planet".

    (And besides, if Pluto is going to be the dwarf planet, which planet do the elves get? Or the hobbits? Won't someone think of the hobbits?)

  • The discovery of Sedna and 2003 UB313, both of which are very close to Pluto in size. This means Pluto is the same category of small rocky planets as Sedna and 2003 UB313, so it can't be considered the same category of planets as the other eight known planets.
  • Napoleon... (Score:3, Funny)

    by turthalion (891782) on Thursday August 24, 2006 @10:54AM (#15969762) Homepage

    I guess we can drop the 'Period' from 'Mary's violet eyes make John stay up nights.'

    I don't like this at all.

    You IAU bastards! Now, My Very Educated Mother no longer Just Sat Under Napoleon's Picture. Now, My Very Educated Mother Just Sat Under Napoleon.

    You guys are sick. Leave my mother out of this.

  • from TFA

    "Brown was pleased by the decision. He had argued that Pluto and similar bodies didnt deserve planet status, saying that would take the magic out of the solar system.

    UB313 is the largest dwarf planet. Thats kind of cool, he said."

    cool?
  • by telchine (719345) on Thursday August 24, 2006 @10:57AM (#15969782)
    Gustav Holst was right all along!
  • We must immediately declare WAR on any objects in Plutos vicinity to help it restore its status as a planet.

    Oh yeah, and couple billion tons of mass as development aid wouldn't hurt, either.

  • Mary? (Score:2, Informative)

    by gafferted (560272)
    Most volcanoes erupt mulberry jam sandwiches under normal pressure

    Andrew

  • by js3 (319268)
    from my point of view, they didn't want pluto to be classified a planet so they created a definition which excluded pluto. I mean I can create a defintion of human that excludes certain races, it doesn't make me any less wrong.
    • The problem here is that there isn't a scientific definition that would... a) include pluto b) exclude everything else. Thusly, any definition at all (other than 'because its tradition') would cause a change in the rankings. This change is actually the one with the least strange fallout... the nearest other alternative ended up creating 3-4 extra planets, possibly including the Moon.
  • Before Pluto was discovered, there was "Mother Visits Every Monday and Just Stays Until Noon". (Note that the "and" covers the asteroid belt!) Adding Pluto changed this to "...Until Noon, Period". I propose we just go back to the original.
  • Anyone? Anyone? (Score:4, Interesting)

    by darkitecture (627408) on Thursday August 24, 2006 @11:06AM (#15969837)
    Quick, someone who actually knows what they're doing, please give me a rough answer/calculation to the following queries:

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

    1) - Is it possible for Pluto and Neptune to one day (like within the next couple billion years) collide? Or are their respective orbits degrading to the point where by the time they'd be near each other orbit-wise, their orbits would no longer overlap significantly? Or by 'overlap' do they mean "diagrammatically speaking, on a two-dimensional representation they overlap but even at their closest possible point they're still a squillion miles away from each other"?

    2) - If so, how cool would that be? Would it be funny enough to make it onto an America's Funniest Home Videos video montage? Would it need special clown-horn-honking sound effects?

    3) - Considering their distance from Earth and their relatively small size, would a collision of the two have any noticeable effect here on Earth?

    4) - Seriously, how cool would worlds colliding be?! Costanza jokes aside, I think it'd be awesome to the max.

    • Re:Anyone? Anyone? (Score:4, Informative)

      by Nemosoft Unv. (16776) on Thursday August 24, 2006 @11:18AM (#15969945)

      Is it possible for Pluto and Neptune to one day (like within the next couple billion years) collide?

      Nope. Their orbits are in 3:2 orbital resonance [wikipedia.org]; basicly this means they constantly miss each other (a bit like your average commuter bus and train schedule :P). Also, due to the declination of the Pluto orbit it doesn't even touch the Neptune orbit. When seen straight from above, the orbits overlap, but if you go off-angle to just the right spot the Pluto orbit can be seen to be completely separated from Neptune.

    • by damburger (981828)
      Some kind of orbital resonance means they can't collide unless their orbits change at some point in the future.
    • Re: (Score:2, Informative)

      by noretsa (995866)
      1) No. First off, while at one point Pluto is closer to the Sun than Neptune and all 2D maps show the orbits crossing, in 3D the orbits do not intersect. Secondly Pluto is in a resonance with Neptune (I think 2:3), so any orbital deviations will be "corrected" by Neptune resulting in a stable solution for billions of years. Eventually they will lose enough energy through gravitation radiation to start migrating inward towards the sun's dead corpse but who knows what the solar system will look like by th
    • 1. No. The orbits do not overlap if you look at them three dimensionally. As for colliding, that's not going to happen since Pluto is locked in a 3:2 resonance with Neptune, which is very stable. Basically, for every 3 Neptune orbits, Pluto completes 2 orbits. These are stable on timescales of billions of years (which is why Pluto is observable today rather than having collided with Neptune billions of years ago).
      2. Yes, it would be interesting (maybe not funny, though)
      3. It probably wouldn't have an
  • Nine little planets, orbiting around the Sun, one was deemed too small, and then there were eight...
    Eight little planets, orbiting around the Sun, one was deemed too big, and then there were seven...
    Seven little planets, orbiting around the Sun, one had too many rings, and then there were six...
    Six little planets, orbiting around the Sun, one got too close and melted, and then there were five...
    Five little planets, orbiting around the Sun, one got too cold and froze, and then there were four...
    Four little p
  • You know what the problem with this "What is a Planet?" debate. There is no metric. It is the case, and always has been, that whether or not something is a "planet" is a matter of almost complete subjectivity. There is still no objective, measurable and testable model under which an object can be said to be a planet.

    In programming terms, the function:

    bool Is_Planet( Astronomical_Object* foo );

    , does not yet exist. Well, under some proposals, it would have existed in the following form:

    bool Is_Planet( Astron
  • Pluto's been demoted.

    That's exactly what it would like us to think...
  • Beyond the fact that Clyde Tombaugh got eyestrain looking at photogrpahic plates trying to find the damned thing in the first place (he's doing 7200 RPM in his grave as we speak - people in Las Cruces can hear the high-pitched whine), the fact is we all grew up thinking of Pluto as a planet and this whole fracas has been nothing but a circus of uptight astronomers, lame-brained reporters, and fringe wackos.

    I for one am not going to give in -- Pluto's a planet, case closed. When we go whippinng through oth

  • It is sad but at least they are consistent; an object should have cleared debris from its formation to become a planet; without these, Ceres and several astroids would have been planets as well.
  • I guess Pluto DOES know when to quit...
  • Pluto and Neptune (Score:3, Insightful)

    by thundergeek (808819) on Thursday August 24, 2006 @11:22AM (#15969981) Journal
    FTA - "Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's." and from the definition, "and has cleared the neighborhood around its rbit."

    Doesn't that mean that Neptune also hasn't cleared it's neighborhood? It's orbit overlaps that of Pluto. So why is IT a planet?
  • ..as sales increase! at least for a short time.

    does anyone know if this ruling applies in kentucky? given that whole "evolution is just a 'theory'" thing and all..

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