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Pluto's 3 Moons and a Probe to Study Them 143

It doesn't come easy writes "For those of you keeping score, Pluto now officially has three moons, with more possibly to follow. The newfound moons orbit about 27,000 miles (44,000 kilometers) from Pluto, more than twice as far as Charon, Pluto's other satellite. They are 5,000 times dimmer than Charon. The moons were found using the Hubble Space Telescope. For now, Pluto is the only Kuiper Belt object known to have satellites. Some nice images of Pluto and its moons are included in links. Enjoy!" Relatedly IZ Reloaded writes "NASA says the Atlas 5 rocket that will carry the New Horizons Pluto probe has suffered slight damage thanks to Hurricane Wilma. New Scientist reports: "The Atlas 5 rocket stands within a construction hangar at Cape Canaveral Air Force Station on Florida's east coast. As Wilma rolled though the region on 24 October, fierce 122-kilometer-per-hour winds tore holes in the hangar's 83-meter-tall door and caused minor damage to the rocket inside.""
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Pluto's 3 Moons and a Probe to Study Them

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  • Now that Pluto's been confirmed to have more than one moon, what will than mean for the old debate over whether Pluto or Charon's the actual planet? Ought to be fun to watch...
    • I am not a pro astronomer or anything, but I am always fascinated by this stuff. Particulary in this case, although I don't have any emperical data, if I had to guess I would say Pluto/Charon + moons started as a single Kupier object or planet, but some catastrophic impact caused the original object to shatter into these pieces, so technically it would all be one object right? Anyhow my thought process for this theory is that an object with a mass as small as what Pluto has is unlikely to have gathered th
  • Hey now! (Score:4, Funny)

    by rackhamh ( 217889 ) on Monday October 31, 2005 @05:29PM (#13918780)
    There will be no moon probing while I'm around!
  • No confirmed (Score:3, Informative)

    by Anonymous Coward on Monday October 31, 2005 @05:29PM (#13918786)
    So not official. RTFA. That's no moon....that's a canditate.
  • Nice? (Score:5, Interesting)

    by lucabrasi999 ( 585141 ) on Monday October 31, 2005 @05:30PM (#13918792) Journal
    some nice images of Pluto and its moons are included in links

    Nice? The photographs are a bunch of small white dots! Does anyone else see real photographs? I guess he is referring to the "artistic conceptual drawings"

    • Nice? The photographs are a bunch of small white dots! Does anyone else see real photographs? I guess he is referring to the "artistic conceptual drawings" imho the quality of the pictures is kinda nice. you can clearly see the objects and that's what counts
    • Re:Nice? (Score:5, Insightful)

      by l2718 ( 514756 ) on Monday October 31, 2005 @05:47PM (#13918916)
      A bunch of small white dots is very good, actually. The fact that both Pluto and Charon come out as extended objects in the short exposure picture is quite impressive in its own right. I wonder if the long exposure has better resolution or is smeared due to an imprefect correction for the relative motion of the telescope and Pluto. Any astronomers reading this?
    • Re:Nice? (Score:3, Informative)

      by Black.Shuck ( 704538 )
      Does anyone else see real photographs?

      The Wikipedia is currently exhibiting the best true-color image of Pluto to date:

      http://en.wikipedia.org/wiki/Pluto [wikipedia.org]
    • Re:Nice? (Score:4, Informative)

      by einhverfr ( 238914 ) <[moc.liamg] [ta] [srevart.sirhc]> on Monday October 31, 2005 @06:19PM (#13919190) Homepage Journal
      Nice? The photographs are a bunch of small white dots! Does anyone else see real photographs? I guess he is referring to the "artistic conceptual drawings"

      I disagree. For those of us who get excited about these things, they are actually really cool. For anyone who spends much time in front of a telescope, these are quite exciting.

      Now, in terms of whether Pluto is a planet or not... It is clear that it did not form from the same planetary disk that spawned the planets from Neptune on in. It does not appear to be made of the same material, nor does it appear to be close to the plane of the ecliptic. Mars's moons are different and were clearly captured as well though probably from the asteroid belt where planetary formation was disrupted by the gravity of Jupiter (though I suspect that our moon was formed along with the earth in the same band-- the fact that the moon is a near perfect sphere, and that it is within a couple degrees of the ecliptic support this hypothesis I think better than the idea that either the moon was ejected from the earth or that it was captured). Pluto as the nearest of the large KBO's provides many opportunities to study issues involving comet formation and even the dynamics which may have brought the precursors of life to our planet.
      • How does the moon's distinct lack of heavier elements fall in line with the moon being created at the same time? The mars-sized-object striking a young, hot Earth and ejecting the materials one would find in our crust (rather than the iron and nickel and what-have-you in the center) explains the composition part extremely well. I'm not so sure both the Moon and the Earth forming at the same time would result in the same composition we have here (and I was under the impression quite a few computer models "
        • How does the moon's distinct lack of heavier elements fall in line with the moon being created at the same time?

          Well, there are usually two aspects to the impact ejection theory. The idea is that the earth was struck and:
          1) ejected dust that formed the moon and
          2) knocked the earth's axis so that it we have the tilt that generates the seasons.

          Now, there are two issues that I have with this theory:
          First, it presumes that the earth's equator was very close to the ecliptic. This is not something I can take
          • by Razor Sex ( 561796 ) on Tuesday November 01, 2005 @12:58AM (#13921405)
            1) The impactor, known alternately as Orpheus or Theia, has been modeled to have been about the size of Mars, and to have hit Earth at a very oblique angle. 2) The absolute best evidence we have for the theory is that the moon has essentially no iron core. All the other terrestrial planets do. As it turns out, the comosition of the moon is remarkably similar to that of Earth's mantle (oxygen/silicon). It is theorized that most of Theia's core merged with our own. Earth's mean density is, if I recall, something on the order of 5500 kg/m^3. The moon has a mean density of something like 3300 kg/m^3. If you were to take out the Earth's iron/nickle core and replace it with mantle material, it would have a mean density similar to that of the moon. 3) As an astronomy minor and having taken planetary formation courses, I've never heard anything about carbonaceous chondrite cores forming the basic building blocks of planets. Carbon, counterintuitively, isn't even too abundant on Earth. Or anywhere else for that matter. Or rather, there certainly is a lot of it, but not compared to oxygen, silicon, iron, aluminum, etc. 4) You can't compare the models of planetary formation in the inner solar system to the outer. Not on a 1:1 basis. The outer planets are significantly larger than the inner because they formed past the frost line (about halfway through the asteroid belt). After this line, ice stays in crystalline form, allowing the rocky starts of the other planets to aggregate much more mass, both planetary and gaseous (the rocky core of Jupiter, at least, is probably about 20 times the size of Earth). With this much more mass, they can more easily capture smaller planetismals, which become moons. It would be far, far easier for a Jupiter to capture Luna than for Earth. 5) As alluded to in the beignning of this post, computer simulations have been done on both the capture and impact theories (including many variations of). The impact theory works. The capture does not. 6) That we have plate tectonics, significant ocean basins, etc, could also be construed as evidence for the giant impact theory. Venus has no moons, and there is little evidence that it ever underwent plate tectonics. The same goes for Mars, and I assume Mercury, though I am not sure on the latter. But the most important thing here is #2. That's the smoking gun.
          • I'm not an astronomer either, having just taken a couple of courses in college, but my professors seemed to frame the massive impact theory as more 'the best explanation we have for right now.' It had the advantage of explaining things like the size of the moon, the composition, its unusual distance and orbital velocity (which just don't fit for a capture). It's not perfect (especially if the larger solar system creation model doesn't hold up), but it's the only explanation that doesn't have especially gl
          • I also am not an astronomer, so this may be a dumb question, but how do you get an axis tilt of 177.36 degrees? Surely this is a tilt of 12.64 degrees. So do you use the magnetic poles as the reference; but in that case, when Earth switchs it's magnetic field, will all these axis tilts then be incorrect, or what if the other planets also have magnetic fields which switch?
            The other alternative I see is on direction of rotation, but if that is the case, Venus also has an equator near the elliptic - just spin
      • ... I suspect that our moon was formed along with the earth in the same band-- the fact that the moon is a near perfect sphere, and that it is within a couple degrees of the ecliptic support this hypothesis I think better than the idea that either the moon was ejected from the earth or that it was captured

        The most plausible theory for the formation of the Moon is that the earth was hit by a Mars-sized body, and a bit proto-earth mantle blobbed up, found its way into orbit, and became the moon.

        The capt

        • The most plausible theory for the formation of the Moon is that the earth was hit by a Mars-sized body, and a bit proto-earth mantle blobbed up, found its way into orbit, and became the moon.

          But this theory was mandated by a theory (that carbonaceous chondrites were the original planetessimals) that has suffered some serious setbacks in the last couple of years. The question is: If the moon was co-formed with the earth, why are the elemental makeup of the body so different? The answer that the impact the
          • But this theory was mandated by a theory (that carbonaceous chondrites were the original planetessimals) that has suffered some serious setbacks in the last couple of years. The question is: If the moon was co-formed with the earth, why are the elemental makeup of the body so different? The answer that the impact theory postulates is that the moon was formed by material from the Earth's crust.

            Interesting, what are the setbacks? As for the composition differences, there basically automatic in the theory.

            • Re:Nice? (Score:3, Informative)

              by einhverfr ( 238914 )

              Interesting, what are the setbacks?


              Take a look at http://carnegieinstitution.org/news_980917.html [carnegieinstitution.org]

              The basic problem is that the iron/silicon ratios of C1 carbonaceous chondrite meteorites matches the composition of the earth, but new data from the Pathfinder is raising doubts as to whether Mars has the same ratios (as previously thought). If this data continues to hold up it means that C1 carbonaceous chondrites may have helped form Earth, but Mars joins Mercury as an inner planet not formed from them. And
              • Take a look at http://carnegieinstitution.org/news_980917.html [carnegieinstitution.org]

                Interesting paper, but doesn't really make a difference to the Moon/Earth compositional difference. It's just saying that the "C1 model" doesn't hold for Mars. If it didn't hold for the moon, then maybe that's because it lost a lot of it's native material during the Earth/Theia [wikipedia.org] impact, and Theia did fit the C1 model--or not. Or maybe the moon is captured, and it does or it doesn't fit the C1 model.

                Conservation of Angular Momentum would pla

          • Phobos and Deimos are thought to be captured asteroids. They are nowhere near the size of Luna, and Mars does exist next to the asteroid belt.
      • It is clear that it did not form from the same planetary disk that spawned the planets from Neptune on in.

        I don't understand this, can you elucidate? Are you saying there was another planetary disk at some other time? Or that Pluto and friends wandered in from interstellar space?

        • I don't understand this, can you elucidate? Are you saying there was another planetary disk at some other time? Or that Pluto and friends wandered in from interstellar space?


          There are other planetary disks around other stars. :-)

          And Pluto probably wandered in from the Kuiper Belt. Not sure if I consider this to be intersteller space or not. But it is certainly outside the rest of the solar system.
          • The Kuiper Belt starts within the orbit of Neptune, and only goes out to 49 AU. This is well within the solar system. The Oort cloud may be as large as 3 light years across.
      • Nice? The photographs are a bunch of small white dots! Does anyone else see real photographs? I guess he is referring to the "artistic conceptual drawings"

        I disagree. For those of us who get excited about these things, they are actually really cool. For anyone who spends much time in front of a telescope, these are quite exciting.

        And there is the problem with the public and science/space in general. They've come to believe that unless it's flashy - it's boring and pointless.

      • Er, the Kupier Belt Objects (including Pluto) formed in the same disk as the rest of us. Where do you think they formed and from what? And the compositions of these bodies are quite consistent with the rest of the planets, provided you realized that there was a temperature gradient in the disk so that the inner parts were hot and ices couldn't condense out of the gases. (Giant planets only have gas envelopes because they're big enough to. If they had never gotten that large, they'd be made of pretty muc
  • by Anonymous Coward on Monday October 31, 2005 @05:33PM (#13918813)
    For now, Pluto is the only Kuiper Belt object known to have satellites.

    My good friend UB313 [caltech.edu] would have to disagree.

    There are actually several known KBOs with moons. Or was the submitter being overly litteral and meant multiple moons?
  • by Anonymous Coward on Monday October 31, 2005 @05:33PM (#13918816)
    Unlike what the poster said, Pluto is not the only one with a moon.
    Various other KBOs do, including Xena :
    http://www.planetary.org/news/2005/xena_moon_1003. html [planetary.org]
    • Indeed. From a different website [spaceref.com] (emphasis mine):

      "If, as our new Hubble images indicate, Pluto has not one, but two or three moons, it will become the first body in the Kuiper Belt known to have more than one satellite," said Hal Weaver of the Johns Hopkins Applied Physics Laboratory, Laurel, Md. He is co-leader of the team that made the discovery.

  • by Yeechang Lee ( 3429 ) * on Monday October 31, 2005 @05:35PM (#13918823) Homepage
    [A] new ninth planet has been glimpsed beyond Neptune, just as those influences had said it would be glimpsed. Astronomers, with a hideous appropriateness they little suspect, have named this thing "Pluto." I feel, beyond question, that it is nothing less than nighted Yuggoth [wikipedia.org] - and I shiver when I try to figure out the real reason why its monstrous denizens wish it to be known in this way at this especial time. I vainly try to assure myself that these daemoniac creatures are not gradually leading up to some new policy hurtful to the earth and its normal inhabitants . . . Sometimes I fear what the years will bring, especially since that new planet Pluto has been so curiously discovered.
    "The Whisperer in Darkness [snm-hgkz.ch]" (1930)
    I hope we have our XK-PLUTO [infinityplus.co.uk] nuclear-powered bombers ready for the Old Ones. Me? I'm going to take a little trip to XK-Masada.
  • Or (Score:5, Funny)

    by Rosco P. Coltrane ( 209368 ) on Monday October 31, 2005 @05:36PM (#13918834)
    Pluto now officially has three moons

    More like "four big asteroids are gravitating around each other beyond the orbit of Neptune".
    • ...it's not even official yet. The objects are believed to be orbiting Pluto, but there has been no independent confirmation they actually are, and the IAU hasn't (yet) responded to the submitted claim.
      • by Rosco P. Coltrane ( 209368 ) on Monday October 31, 2005 @05:42PM (#13918878)
        ...it's not even official yet

        Okay then: "two big asteroids are known to be orbiting around each other beyond Neptune, but two more are presumed to have joined the party, which incidentally pisses Neptune off to high heavens".
        • Ah, but Neptune is inside Pluto's orbit, so isn't in as high a heaven as it was in. :) And if the Romans were anything to go by, the only thing pissing Neptune off would be that it wasn't invited.


          Incidently, the CNN report mentions that the astronomers called them the Halloween Moons - I didn't know Eric Raymond was an astronomer!

    • by Rei ( 128717 )
      If Pluto had captured asteroids, that would be huge news ;) Talk about a funny game of orbital billiards....

      • by jd ( 1658 )
        ...on where it kept them. The underworld is a BIG place to hide things you don't want discovered.
  • Remember (Score:1, Funny)

    by eclectro ( 227083 )

    Pluto is a planet, not an object. Anything else is either cultural revisionism or solar system wide discrimination.
  • by Viper Daimao ( 911947 ) on Monday October 31, 2005 @05:40PM (#13918865) Journal
    Does that mean we can call them "Cerebus" collectively?
  • Classification (Score:4, Insightful)

    by Da3vid ( 926771 ) on Monday October 31, 2005 @05:43PM (#13918892)
    Is it really a big deal when we name something a moon? Its just a matter of relativity. A planet, a moon, an asteroid, a rock... they're all the same thing, that varies by degrees. I suppose the things orbital path is of interest, but how much can we really learn just by applying labels? We didn't learn anything about the true scientific nature of those bodies, we just named them. I think I'll name them Susanna, Melinda and Jim.

    -Da3vid-
    • Re:Classification (Score:3, Informative)

      by Rei ( 128717 )
      A body having at least one moon is very important for astronomers. By observing even a distant moon, you can get a good fix on its orbital dynamics. Knowing its orbital dynamics, you can determine with a good degree of accuracy how massive the body that has the moon is.

      There are all sorts of other benefits moons provide, by the way, as far as astronomy goes, from their chemical properties compared to those of the parent, to their diffraction of light from stars behind them.

      Having multiple moons isn't as i
      • "Having multiple moons isn't as important, but does raise some interesting questions;"

        Actually, that isn't true. Particularly in the case of Pluto. Multiple moons certainly help refine mass measurements in the general case. In the case of Pluto, Charon is so large (compared with the parent) that you don't GET the mass of Pluto from an orbital period/distance measurement, you get the mass of combined system. (Technically, this is always true. But for most bodies, including all of the planets, the mass o
        • My claim was that it "isn't as important". Lets look at the mass estimate for a moonless body, such as Quaoar: mass estimates I've seen for Quaoar range from 1.0e21 to 2.6e21 kg. Pluto, mostly thanks to Charon (although it helps that it's larger and closer) is known to, what, 1% or so? The majority of the mass clarification comes from the first moon discovered.
          • It is actually pretty important. Quaoar's mass doesn't tell us that much, overall. The relative masses of Pluto and Charon are keen to constraining models of Charon's formation, something we're pretty keen on doing.
            I believe that the error on the mass of Charon is around 5-10%, actually. But I'd have to look that up to be sure since it's been years since I've let it keep me awake at night.
      • Heres something I've been wondering about.

        We can detect and confirm solar system celestial bodies by spotting what we think is a new object then, if I understand this right, working out where it would have been x number of years ago and looking for it on photos from that time.

        If it shows up on the old photo where you predicted it would be, this confirms that you have a new object, right?

        This makes me wonder how effective we would be at detecting asteroid-sized objects moving around in the solar system under
    • That is why (Score:3, Insightful)

      by jd ( 1658 )
      I would be in favour of a classification system that DID mean something. For example, we know that the composition of all the rocky planets we've investigated and all of the Gas Giants is mixed. We also know they have a single core. Neither of these is proven (or disproven) for Pluto, but could be tested. We know that the composition statement is false for all asteroids and the single core is false for all comets. It would seem easy enough to base a classification system on such parameters.

      Would this help u

      • Re:That is why (Score:3, Informative)

        Oops, a lot of this is based on faulty data.

        First, we don't know that all eight planets have cores. The biggest of the lot, Jupiter, is currently an unknown. A new mission is in the works to test precisely this issue, though.

        Second, some asteroids DO have cores. And we're pretty certain that many more used to because that's where the metal-rich asteroids came from. (Break-up of larger asteroids which had differentiated.)

        Now, I'm not sure what you mean when you say that the "composition is mixed", but I
  • Kinda small... (Score:1, Insightful)

    by Fermatprime ( 883412 )
    These "moons" are only 30 and 100 miles across. Mars' Phobos and Deimos, widely thought to be captured asteroids, are thousands of kilometers across. These are PUNY. If we could somehow gather up all the junk orbiting Earth and pack it together, we'd probably have a "moon" about that size, too.
    • Re:Kinda small... (Score:4, Interesting)

      by l2718 ( 514756 ) on Monday October 31, 2005 @06:01PM (#13919030)
      These "moons" are only 30 and 100 miles across. Mars' Phobos and Deimos, widely thought to be captured asteroids, are thousands of kilometers across.

      You are way out of the ballpark, I'm afraid. These two new moon are larger than Phobos (diameter approx. 22Km) and Deimos (diameter approx. 12Km). The Earth (and its moon) Mars, Venus, Mercury, the Galilean Moons and Titan are thousands of kilometers across, but everything else is much smaller. Ceres (the largest asteriod) is only 914Km across.

    • Failed to compile: Mixed types in context of comparison!
    • http://www.solarspace.co.uk/Mars/phobosdeimos.php [solarspace.co.uk]

      Bzzt, hate to correct you, but Phobo and Deimos are TINY
      Phobos - 22.2km diameter
      Deimos - 12.6km diameter

      Hardly thousands of kilometers across and if they're going to be "moons" why not Plutos?

    • by geoswan ( 316494 ) on Monday October 31, 2005 @06:18PM (#13919181) Journal
      What!

      Even if you rolled all the rockets we have ever launched, and all the fuel we packed into them, I doubt it they would form a sphere even a single kilometer in diameter.

      A Saturn V was about 20 meters in diameter, and about 100 meters tall, more or less. Volume of a cylinder is pi r^2 * length. That would make the volume of a Saturn V about pi * 2500 meters^3.

      The volume of a sphere is 3/4 * pi r^3. The volume of a sphere one kilometer in diameter would be pi * 93,750,000 meters^3. That would be volumne of something like the prelaunch volume of 37,000 Saturn Vs. The payload of a rocket is a fraction of the mass of the entire thing. Let's say 1%. Most rockets are much smaller than a Saturn V. Payloads launched into low earth orbits decay within decades, like Mir, or Spacelab.

      It wouldn't surprise me if the volume of all the working satellites, and space detritus, that remain in orbit would be less than the prelaunch volume of a single Saturn V.

    • Re:Kinda small... (Score:2, Interesting)

      by K.B.Zod ( 642226 )
      The best thing Earth has after Luna in terms of a moon is probably Cruithne [wikipedia.org], and that doesn't even count as a satellite anyway.
  • The slashdot article says Pluto is the only Kuiper Belt Object to have a moon. Not so: Tenth Planet Has A Moon [sciencedaily.com]
  • has really caused us a lot of grief in classifying heavenly bodies and discovering them. Not only does it interfere with scientific terminology, it hampers understanding of average people. We should just kick Pluto out and accept that we have 8 planets, not 9. Everyone would be happier (except Pluto).
    • Not only does it interfere with scientific terminology...

      Which termionology is that? Are you saying that there is a widely accepted definition of a planet that is not in the center of a controversy? Please, do tell. What is it?

      (there isn't one, don't bother trying to find it)

      If it were as cut and dried as referring to the definition of the term "planet" there'd be no controversy. Pluto would fit the definition, or it wouldn't. But there isn't a definition that has gained enough acceptance to settle the
  • As Wilma rolled though the region on 24 October, fierce 122-kilometer-per-hour winds tore holes in the hangar's 83-meter-tall door

    Oh please, 'twas but a mere breeze. That hangar's falling apart anyway.
  • All right, I can understand that Jupiter, Saturn, Uranus and Neptune have zillions of moons because they're big mommas with a lot of gravity, and when you're very generously rounded -- well, you just naturally attract a lot of trash. Fact of life.

    But now even puny Pluto is getting into the act. Three moons, when Mercury has zero and Mars but two. What gives? Why are moons more common in a general way in the outer Solar System than the inner? This is odd. Is it all captured from the Kuiper Belt? Did
    • Well, you really only have Pluto to draw on for the outer solar system that isn't a jovian planet. There are a few KBOs with moons, but we also know of a LOT of KBOs. (... But we don't *know* how many of those might have moons, I don't think. They're awfully faint.) So it's a big vague. But a very insightful question :-)

      The answer is: it's easier to capture objects in the outer solar system because the spheres of influence are larger. To get into the region of space where Earth's gravity dominates ove
  • Is this just an attempt to keep Pluto in the "planet" catagory? Because it seems like someone says "So what makes Pluto so special? We've got dozens of KBOs that big and bigger" and some people refuse to consider the idea that Pluto is nothing special. Now we suddenly have 3 moons on Pluto?

    I don't know. I'm probably just crazy, but it seems possible to me.
  • "As Wilma rolled though the region on 24 October, fierce 122-kilometer-per-hour winds tore holes in the hangar's 83-meter-tall door and caused minor damage to the rocket inside."

    Can we have this in imperial units, this is an American website and an American space program we're talking about here...

  • The Mi-Go might find out about us...

    I'm afraid of their brain canisters!

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