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Thread: Two moons discovered orbiting Pluto!

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    Exclamation Two moons discovered orbiting Pluto!


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    Hubble press release

    The new satellites orbit Pluto in similar orbits about two to three times as far as Charon, and are between 45 and 160 km in diameter. They were easily spotted by Hubble, which wasn't earlier given observing time to conduct the search.

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    This is getting weird. Does this mean that Xena, Sedna and Quaoar probably have multiple systems too?
    "Occam" is the name of the alien race that will enslave us all eventually. And they've got razors for hands. I don't know if that's true but it seems like the simplest answer."

    Stephen Colbert.

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    Be sure to read the release carefully.....for now they are still saying "possible moons." It's not confirmed that they are actually there. They were observed 2 times in May, and confirmation will come follow-up observations in February. Then the name game through the IAU begins!

    I hope it's true--how exciting this would be! I bet NASA wouldn't make such a release if they weren't pretty confident about it.

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    Wow! So the Hubble telescope easily found these new moons once it was finally given a chance. Goes to show what can happen once one gets past all the red tape.

    Hopefully this will strengthen the arguements favoring a servicing mission to Hubble, and allowing it to explore the Kupier Belt region.
    And really strengthen support for the New Horizions probe.

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    Yeah, this discovery is almost secure.

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    You will now start paying proper homage to
    Percival Lowell whose meticulous mathematical
    investigation into remaining anomalies in the
    orbit of Uranus led to the discovery of Pluto.
    The exact reason remains obscure but hordes
    of lightweight astronomy hacks should not be
    allowed to triumpth in downgrading his
    achievement!

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    Great news! Now we definately need to do a flyby. I bet thery're really cute.

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    Talking

    This is the first piece of astronomical news that has actually amused me! It sure looks as if Pluto is fighting for its status as a planet.

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    Does being in the Kuiper Belt give Pluto an advantage as far as capturing moons is concerned. How hard have astronomers looked at whether or not the larger asteroids have moons?
    Everything I need to know I learned through Googling.

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    Quote Originally Posted by Disinfo Agent
    This is the first piece of astronomical news that has actually amused me! It sure looks as if Pluto is fighting for its status as a planet.
    Indeed! And if you thought these new satellites were really small, they are actually much larger (several times!) than Mars' puny moons. And larger than almost every irregular satellite around the giant planets.

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    One thing about this really amuses me: back in high school I was clearing out my otherwise wonderful educational establishment's woefully inadequate library, and discovered a book on the solar system from oh, about 1957. In it, I found a small sentence that has stayed with me always, and now seems particularly apropos to mention: "Pluto probably has no satellite."
    "Occam" is the name of the alien race that will enslave us all eventually. And they've got razors for hands. I don't know if that's true but it seems like the simplest answer."

    Stephen Colbert.

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    That is the best news I've heard all day!

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    Sweet. This settles it for me. Multiple significant moons, it's a planet.
    "Words that make questions may not be questions at all."
    - Neil deGrasse Tyson, answering loaded question in ten words or less
    at a 2010 talk MCed by Stephen Colbert.

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    Wow. Cool. That just put a little picante sauce in Horizon's enchilada.
    We know time flies, we just can't see its wings.

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    What if we find multiple moons over other KBOs?
    "Occam" is the name of the alien race that will enslave us all eventually. And they've got razors for hands. I don't know if that's true but it seems like the simplest answer."

    Stephen Colbert.

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    They're giving the same orbiting distance for both the new moons. Two moons can't be the same distance unless they're locked in each other's Lagrange 4 & 5 points, which might suggest that there's one more (unseen 4th moon), or that they're in horseshoe orbits like Saturn's Janus and Epimethus.

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    Quote Originally Posted by Kullat Nunu
    Indeed! And if you thought these new satellites were really small, they are actually much larger (several times!) than Mars' puny moons. And larger than almost every irregular satellite around the giant planets.
    Actually, no. It only means that Pluto is indeed located ina busy part of the system, aka Kuiper Disk and is merely a larger component of it. I find that it actually lessens the Planetary status likelyhood, more akin a large binary asteroid with 2-3 moonlets.
    The impossible often has a kind of integrity the merely improbable lacks. -Douglas Adams


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    Quote Originally Posted by tony873004
    They're giving the same orbiting distance for both the new moons.
    Not according to: Background Information Regarding Our Two Newly Discovered Satellites of Pluto
    0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

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    Smile

    Quote Originally Posted by tony873004
    They're giving the same orbiting distance for both the new moons. Two moons can't be the same distance unless they're locked in each other's Lagrange 4 & 5 points, which might suggest that there's one more (unseen 4th moon), or that they're in horseshoe orbits like Saturn's Janus and Epimethus.
    Given the fact that Pluto & Charon are often talked about as an example of a possible `binary' system, I think it fair to say that these two moons would be effected in strange ways by the gravitational influences of Charon & Pluto. In fact, if these two moons are confirmed I think it would be a very interesting exercise working out what their orbits actually are, and indeed, how stable their orbits are.

    For the record though, I think this has no effect on Pluto's planetary status. I think it just re-enforces how little we actually know about that region of space outside the orbit of Neptune.

    To be honest, I think we should remain wary of classifying something like this as unique given that lack of knowledge.

    Despite all that though, it is indeed a very exciting discovery and will definitely help increase interest in the Pluto Express project amongst the general populace. I hope NASA do a decent PR job on that, because with such a long lead time there's a lot of scope for interest to really be coming to a crescendo in 2020 if they can do it properly.

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    Quote Originally Posted by mantiss
    Actually, no. It only means that Pluto is indeed located ina busy part of the system, aka Kuiper Disk and is merely a larger component of it.
    I didn't suggest otherwise. I answered to this: It sure looks as if Pluto is fighting for its status as a planet, which it really does.

    But let's keep discussion on Pluto's planethood in other threads, please!

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    Quote Originally Posted by tony873004
    They're giving the same orbiting distance for both the new moons.
    They're just imprecise. BA told in his blog that they orbit at 50,000 km and 65,000 km from Pluto.

    BTW, the discoverers' webpage is online and has lots of information about the moons and their discovery.

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    Quote Originally Posted by mantiss
    Actually, no. It only means that Pluto is indeed located ina busy part of the system, aka Kuiper Disk and is merely a larger component of it. I find that it actually lessens the Planetary status likelyhood, more akin a large binary asteroid with 2-3 moonlets.
    I'd be interested to know whether they orbit Pluto exclusively, or if they orbit the barycenter between Pluto and Charon. Another question is are they orbiting Pluto equatorially or are they off kilter at all. Again, this goes back to the issue of gravitational dominance, kinda tangent to the Planet vs. KBO issue.

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    Quote Originally Posted by ToSeek
    Does being in the Kuiper Belt give Pluto an advantage as far as capturing moons is concerned. How hard have astronomers looked at whether or not the larger asteroids have moons?
    This is an interesting question. It's easier to jump in a pickup the slower it goes. Wouldn't the slower orbital speeds allow for easier "pick-up"?

    BTW, a 45 km object at Pluto seems to be equivalent in apparent size to an 8 km object at Jupiter. This is about the size of some new Jupiter moons, IIRC.
    We know time flies, we just can't see its wings.

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    Quote Originally Posted by Doodler
    I'd be interested to know whether they orbit Pluto exclusively, or if they orbit the barycenter between Pluto and Charon. Another question is are they orbiting Pluto equatorially or are they off kilter at all. Again, this goes back to the issue of gravitational dominance, kinda tangent to the Planet vs. KBO issue.
    They orbit the system barycenter, of course. Because Charon is so large the Pluto-Charon barycenter lies well outside Pluto. The new satellites are small (thousands of times less massive than either Pluto or Charon), so the barycenter of the whole system is basically the same as the Pluto-Charon barycenter.

    Here's a diagram of the Pluto system as seen from the Earth:


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    Quote Originally Posted by George
    BTW, a 45 km object at Pluto seems to be equivalent in apparent size to an 8 km object at Jupiter. This is about the size of some new Jupiter moons, IIRC.

    No, the comparison will be on a vastly different scale. If you do some size comparisons between planet's and their moons in the solar system you will see that an object 45km found on Pluto is big compared to Pluto.

    Calculations (all calculations are done in km):

    (size of satellite/size of planet)=size percentage

    Earth is 12756.3km, the Moon is 1738km so:
    1738/12756.3= ~13.63% Moon to Earth

    Jupiter is 142984km, Ganymede is 2631km:
    2631/142984= ~1.84% Ganymede to Jupiter

    Pluto is 2274km, Charon is 1172km:
    1172/2274= ~51.54% Charon to Pluto

    New mooons of Pluto maybe 45-160km big:
    45/2274= ~1.99% lower size limit of new moons to Pluto
    160/2274= ~7.04% upper size limit of new moons to Pluto
    "New" moons found around Pluto can be from 1.99% to 7.04% size of Pluto


    So you take the percentages of the "new" Pluto moons and plug them in with Jupiter, you'll get something like this:

    142984x1.99%= 2829.5km equivalent sized object

    142984x7.04%= 10066.1km equivalent sized object


    This means that the "new" moons of Pluto are big compared to Pluto. So if a 45km moon orbits Pluto it'll be the equivalent of finding a moon abit bigger than Ganymede orbiting Jupiter. If the upper size limit is used you'll get something of a moon about the size of Earth (10066.1km) orbiting around Jupiter. This moon will be smaller than Earth, but still a good sized "planet" still.

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    Does anyone else think this two Hubble photos are weird? It gives the impression of a plan view of the Pluto region... How can this been done? Pluto isn't that far off the ecliptic that orbiting feature appear top-down viewed.

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    That's an interesting comparison, Vhear. Thanks.

    However, I was really suggesting that Hubble, given operating time, might have a number of new moon discoveries. If it can see a 45 km object at Pluto, it should be able to see an 8 km object at Jupiter (assuming similar albedo). [However, I am not known for being always right around here, but, hopefully, at least stimulating. ]

    I believe the apparent size [edit: diameter] equates to about .002 arc seconds. (Of course, this is beyond Hubble's resolution so it is seeing a "point source", I suppose)
    Last edited by George; 2005-Nov-01 at 06:12 PM.
    We know time flies, we just can't see its wings.

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    Quote Originally Posted by Joff
    Does anyone else think this two Hubble photos are weird? It gives the impression of a plan view of the Pluto region... How can this been done? Pluto isn't that far off the ecliptic that orbiting feature appear top-down viewed.
    Its both off the ecliptic with an axial tilt, its probably giving us a very oblique view through the system thats more perspective than plan.

    Kullat's diagram shows a very distorted ellipse representing the orbital tracks of the system where the actual orbits are likely far more circular.

    By the way, thanks for that. I figured it likely was the barycenter, but I'd rather ask and be sure. Besides, that is a pretty awesome diagram.

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    Quote Originally Posted by Joff
    Does anyone else think this two Hubble photos are weird? It gives the impression of a plan view of the Pluto region... How can this been done? Pluto isn't that far off the ecliptic that orbiting feature appear top-down viewed.
    JPL Solar System Simulator :: Pluto, from Earth, May 15, Body 2%, show orbits
    0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

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