Forgot your password?
typodupeerror
Space Science

Pluto Might Be Bigger Than Eris 257

Posted by Soulskill
from the but-does-disney-have-a-trademark dept.
astroengine writes "Look out, the battle of the dwarf planets is about to re-ignite! During last weekend's rare occultation of a star by Eris, astronomers managed to gain one of the most accurate measurements of Eris' physical size. When three Chilean telescopes watched the star blink out of sight, astronomers were shocked to find that Eris is actually a lot smaller than originally thought. So small that it might be smaller than Pluto. On speaking with Discovery News, Eris' discoverer Mike Brown said, 'While everyone is more interested in the "mine is bigger than yours" aspect, the real science is the shockingly large density of Eris.' The mass of Eris is well known, so this means the object is more dense than Pluto. Does this mean the two mini-worlds have different compositions? Did they evolve differently? In light of this finding, is the underlying argument for Pluto being demoted from the planetary club on wobbly ground?"
This discussion has been archived. No new comments can be posted.

Pluto Might Be Bigger Than Eris

Comments Filter:
  • Requisite (Score:2, Funny)

    by Enderandrew (866215)
  • by Pojut (1027544) on Friday November 12, 2010 @04:59PM (#34210826) Homepage

    This sounds about right; the Eris is a fairly tiny phone.

    Oh wait...

  • Pluto controversy (Score:3, Interesting)

    by falldeaf (968657) <falldeaf&gmail,com> on Friday November 12, 2010 @04:59PM (#34210832) Homepage
    I remember being so confused about the Pluto controversy. Maybe it's just because I'm not an astronomy nerd but I don't understand the uproar about correcting a miss-classification of a heavenly body... I remember Neil Desgrasse Tyson on the Colbert Report chiming in that it was just a simple fact. Any of you astronomy nerds reading that could explain the emotional reaction? (Not to assume, was it astronomy nerds that were upset? Maybe it was Astrology people that were upset.)
    • by just_another_sean (919159) on Friday November 12, 2010 @05:06PM (#34210892) Homepage Journal

      I also seem to remember Neil blaming most of the uproar on Disney. Paraphrasing - "if they hadn't named that darned dog Pluto nobody would have cared".

      It's hard to tell with Neil how serious he was on that one. :-)

    • by fuzzyfuzzyfungus (1223518) on Friday November 12, 2010 @05:11PM (#34210944) Journal
      I think that it has a lot to do with the fact that a shockingly large number of people confuse nomenclature with knowledge. Because of that, a fairly fiddly technical discussion over how best to handle astronomical nomenclature hit the popular press as "zOMG pointy-headed scientists don't even know if Pluto is a planet!!!!!"

      Naming is not a trivial thing, good nomenclature makes the world a much easier place, crap nomenclature makes it a mess wholly without reason; but either way it seduces people into forgetting that names are simply constructs, assigned for our convenience to bundles of real things. Sometimes, you have to revise the constructs to make the nomenclature better, simpler, more expressive, whatever; but that is very different from changing the bundle of real things and attributes.
      • Re:Pluto controversy (Score:5, Informative)

        by sznupi (719324) on Friday November 12, 2010 @05:21PM (#34211034) Homepage

        At least we can be certain it will pass - I don't see any people lamenting that Ceres, Pallas, Juno and Vesta have lost their planetary status.

        Status which they had, for half a century after their discovery. Similar to Pluto.

        (for that matter, the same applies to the Sun - it was also classified as a planet at some point)

        • by Hatta (162192)

          The problem is that nobody was taught a planetary mnemonic that included Ceres, Pallas, Juno, and Vesta. As far as people are concerned if it's in the mnemonic, it's a planet. If it's not, then it's not. Their understanding doesn't go any further than that. To them, saying "pluto isn't a planet anymore" is very much like saying "Q isn't a letter anymore".

          • Re: (Score:3, Funny)

            by rarel (697734)
            Q- "I'm not a letter, I'm a free, uh... alien of nearly infinite power!"

            Star Trek: The Next Generation - The Lost Episodes

    • by Jiro (131519)

      It's not a misclassification. It's not as if they had a definition of a planet and then suddenly figured out that Pluto didn't fit it--that would be a misclassification. Pluto is no longer classified as a planet because they wrote the definition just now specifically to exclude it.

  • by heptapod (243146) <heptapod@gmail.com> on Friday November 12, 2010 @05:00PM (#34210834) Journal

    Size does not matter. Clearing its path matters. Per the IAU Pluto has not cleared its orbital path and can not be considered a planet by the current definition.

    • Re: (Score:2, Informative)

      Size does not matter. Clearing its path matters. Per the IAU Pluto has not cleared its orbital path and can not be considered a planet by the current definition.

      Of course, the problem with this is - neither has Neptune.

      • Re: (Score:2, Informative)

        by Anonymous Coward

        Or Earth, for that matter.

      • Re: (Score:3, Interesting)

        by sznupi (719324)

        The definition is not about vacuuming the neighborhood - bodies there (including Pluto) are completely dominated by the gravity of Neptune, that's what this is about.

        • by MozeeToby (1163751) on Friday November 12, 2010 @05:34PM (#34211150)

          Don't forget the real reason that they wanted to change the definition in the first place: current theory predicts that there are probably hundreds, if not thousands of bodies in the outer solar system with basically the same composition and orbit as pluto, and only slightly smaller. There would be no logical reason to exclude those hundreds of bodies from the list of planets without also excluding Pluto, since there is little qualitative difference between them.

          • by sznupi (719324)

            I was just addressing the mentioned "issue" - but yes, exciting times (*) ahead, with many new discoveries almost certainly awaiting. My personal favorite at this point is Sedna, and not only because the timing (relative to its orbit) of the discovery hints at many such bodies - there's also some slight possibility it formed in another star system.

            (*)Also because IMHO, if we will ever reach the stars, gradual spreading towards and across our Oort cloud (and eventually, after thousands of years, some groups

            • (*)Also because IMHO, if we will ever reach the stars, gradual spreading towards and across our Oort cloud (and eventually, after thousands of years, some groups hitching a ride in the clouds of passing star) seems like the way to go (though embryo colonization also looks practical)

              The sky calls to us -- and if we do not destroy ourselves, we will, one day, venture to the stars.

          • Re: (Score:2, Informative)

            by geekoid (135745)

            actually, that was the reason they wanted a clear definition of 'Planet'. Pluto not being a planet is the results of those discussion, not the cause.

            There would be nothing wrong if the definition included Pluto and all those other similar objects.

            • Re: (Score:3, Interesting)

              by Anonymous Coward

              actually, that was the reason they wanted a clear definition of 'Planet'. Pluto not being a planet is the results of those discussion, not the cause.

              There would be nothing wrong if the definition included Pluto and all those other similar objects.

              That may be true but it's naive to think that the motivation for defining "Planet" didn't color the discussion. The original parent is correct in that this was motivated by the perceived inconvenience of having a large number of bodies that would meet the definition.

              The whole vote was a sham in my opinion, because there were other reasonable definitions that got suppressed in discussion because of the issue the parent is raising. The current definition is ridiculous and completely context-dependent, fuzzy,

            • by CorSci81 (1007499)
              The primary reason for the dwarf planet classification is the sane definition that would have made Pluto and similar bodies planets was based on having sufficient gravity to be spherical. That definition would have expanded the number of planets to a very large number with many of them being bodies in the asteroid belt. Having a planet being defined as a body sufficiently massive to clear its orbit kept the number of "planets" sane and has some practical connection to our current theories and understanding
      • It's obviously not about complete clearing of the path, but rather of, well, dynamic dominance in his part of space. The planets do that, even if some orbit crossing or near orbit asteroids are left. Pluto and Eris are in a whole crowd of crap and have not in any way achieved a dominant position in that crowd of crap. In the end, it's just nomenclature
      • by molo (94384) on Friday November 12, 2010 @05:24PM (#34211052) Journal

        Please compare the total mass of all Neptune-crossing bodies to those gravitationally bound to Neptune. You will clearly find that Neptune has cleared the neighborhood. Neptune has a planetary discriminant of 2.4 x 10^4. A body with discriminant >= 1 is considered a planet.

        -molo

        • Re: (Score:2, Funny)

          by Anonymous Coward

          Neptune has a planetary discriminant of 2.4 x 10^4. A body with discriminant >= 1 is considered a planet.

          Your argument is ridiculous. You have countered an emotionally driven fact-free whine with pertinent scientific information. The correct response in this situation is either "Nuh uh!" or "Your mom!"

        • Re: (Score:3, Informative)

          by khallow (566160)

          A body with discriminant >= 1 is considered a planet.

          Not by the IAU. As has been repeatedly mentioned before, the definition of "cleared the neighborhood" has not been defined by the IAU.

      • by Jiro (131519)

        The way the technical definition of clearing the neighborhood is set up, Neptune does.

        The real problem is that picking clearing the neighborhood in the first place is completely arbitrary. They could have picked "has an atmosphere" and ended up with Mercury being disqualified as a planet. They could have defined Jupiter as a failed star and disqualified Jupiter as a planet. They could have picked a size limit at Pluto's size and we'd have had 10 planets.

    • by Tumbleweed (3706) * on Friday November 12, 2010 @05:32PM (#34211134)

      Yes, let's come up with a definition that excludes Pluto - that way we can exclude Pluto. Makes sense.

      • by CorSci81 (1007499)
        Definitions that are reasonable and include Pluto make the number of things we then have to call planets a rather large number. The current definition has some footing in our understanding of how planets form, which is that bodies like Pluto are essentially the remnants of areas of the solar system that failed to coalesce into planets, namely the Kuiper Belt and Asteroid Belt.
    • Draw a dot, and eight concentric circles. The circles represent the orbits of the planets. Then draw an oval that touches the outermost circle on one end and goes out 2/3rds further on the other end. That's Pluto.

      Below that, draw a straight line corresponding to the width of the circles. Those are the planets viewed edge on. Now draw a straight line tilted 17 degrees. That's Pluto.

      Which of these is not like the other?

    • And then there are other (non-IAU?) considerations, like:
      Its not on the same ecliptic plane as the planets.
      Pluto is not the central mass of its orbital plane. Charon does not directly orbit around Pluto; they both circle around the same point in space (along the orbit around the Sun).
      Pluto has less mass than many planetary satellites (ex. Moon, Ganymede, Titan, Triton).
      Pluto has no traits which differentiates it from the asteroids or KBOs.

      • by bolthole (122186)

        Pluto has less mass than many planetary satellites (ex. Moon, Ganymede, Titan, Triton).

        Mercury has less mass than Ganymede too. So.... it's just a "really big comet, in a very tight solar orbit"? :-)

      • Re: (Score:2, Insightful)

        by operagost (62405)
        While we're making arbitrary distinctions...
        • Jupiter is not a planet because it's too much bigger than the other objects.
        • Uranus and Saturn are not planets because they have rings.
        • Saturn, Jupiter, Uranus, and Neptune are not planets because they're gaseous.
        • Mercury's day is longer than its year.

        Pluto has no traits which differentiates it from the asteroids or KBOs.

        It's spherical. Some KBOs aren't, like my favorite Haumea. Yes, I'm an unscientific idiot.

    • Pluto is mostly made of various ices (like comets) and travels through the Oort Cloud (like comets). It's orbit is highly eccentric and at a tilt (like comets). Pluto is quite clearly a large comet that never made it to the inner Solar System. Also, because of it's companion, Charon, the center of gravity for the two is actually between the two. If it were a planet, it would also be unique in this respect as well.
    • If you put Earth out where Pluto is, it wouldn't clear it's orbit, either.
  • by mbone (558574) on Friday November 12, 2010 @05:36PM (#34211160)

    Don't give Eris out yet. There was a lot of discussion on the MPML about this.

    First, Eris is definitely more massive, by about 28%. They both have satellites with good orbits, so their masses are pretty well determined.

    Second, it is not really that clear that Pluto is really larger than Eris. There have been a number of estimates of Puto's size; by the most recent one presented by Angela Zalucha at the DPS meeting (a radius fit to occultation measurements with a new atmospheric model), Pluto and Eris have roughly the same radius within the respective error bars (1146 +-20 km in diameter for Pluto versus 1170 km for Eris).

    What is more interesting to me is that Eris is dense and very bright - could something as rare as Deuterium snow be covering its surface ?

  • I glanced at my RSS feeds and thought the story title was "Pluto might be bigger than Elvis". Now that would be really big!

  • by Mspangler (770054) on Friday November 12, 2010 @10:45PM (#34213134)

    The goddess of discord is certainly living up to her reputation.

    "So you think you have me all figured out, do you? Heh, heh, heh."

    So how long will it take to get there, how big of a dish will it take to get a signal back, and how much plutonium to power the instrument package and radio to find out what is really going on out there?

If you think nobody cares if you're alive, try missing a couple of car payments. -- Earl Wilson

Working...