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Thread: pluto

  1. #1 pluto 
    ox
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    Sad person that I am, I've been reading about the origin of Pluto on a pseudoscience site, which suggests that it might be a moon that has been released from a planet (Saturn?) in some sort of chain reaction caused by a collision between bodies in the early solar system. Does this have any credibility?


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  3. #2  
    Veracity Vigilante inow's Avatar
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    A good summation with some nice references available here:
    http://en.wikipedia.org/wiki/Pluto#Origins


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  4. #3 Re: pluto 
    Moderator Moderator Dishmaster's Avatar
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    Quote Originally Posted by ox
    Sad person that I am, I've been reading about the origin of Pluto on a pseudoscience site, which suggests that it might be a moon that has been released from a planet (Saturn?) in some sort of chain reaction caused by a collision between bodies in the early solar system. Does this have any credibility?
    This idea has a few problems.
    • How could Pluto have retained or received its spheroid form during a collision?
    • How could Pluto be caught in an orbit after having been ejected around another orbit? It would have needed to loose part of its momentum to be bound again.
    • Why should such a collision have Pluto ejected into a trajectory being coplanar with the planetary plane? This is very improbable.

    So, in essence, I think, this idea is just crap.
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  5. #4  
    Universal Mind John Galt's Avatar
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    Pluto is one of the largest Kuiper Belt Objects, entities left over from the formation of the solar system which form a belt beyond Neptune out to about 50 AU. They are thought to be primitive bodies, planetesimals, left over from the formative stages of the solar system. I suspect that when New Horizons gets there in 2015 we shall learn that Pluto's history is not that simple.

    If the wiki article says anything radically different from the above it will just demonstrate that wikis are not 100% reliable. :wink:
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  6. #5 Re: pluto 
    ox
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    Quote Originally Posted by Dishmaster
    How could Pluto have retained or received its spheroid form during a collision?
    But what about the Giant Impact Theory where our moon was ejected from earth after a collision between the earth and an asteroid or meteor. Eventually the moon's centre of gravity settles all of its particles to end up as a sphere. I must admit however that the moon's large size makes this theory doubtful, and yet I saw it on a scientific tv program recently.
    Is our moon the largest in the solar system with respect to the size of its host planet?
    However, back to Pluto. If not an ancient moon, could it possibly have been a deep space body entering our solar system and getting caught in the sun's gravity?
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    The formation of the moon, as the giant impact theory suggests, assuming I understand it correctly, has the moon forming as a molten body*, just as the Earth was, and likely any of the terrestrial planets. Being molten and massive gravity is able to pull it into a sphere relatively easily since molten material is a liquid and thus very malleable.

    Yes our moon is the largest moon in the solar system with respect to it's parent planet.

    The deep space body being caught by the sun, is from my understanding the best theory we have for why Pluto is where it is, with the orbit it has. I haven't done extensive reading or research into Pluto and its origins however.

    *Edit: The moon being molten coming from the debris thrown off during the giant impact. These particles would have cooled and solidified but as they smashed into each other forming larger and larger bodies the heat and energy from impacts on the moon forming it, would cause it to be molten for most if its formation.
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  8. #7  
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    Quote Originally Posted by Haasum
    Yes our moon is the largest moon in the solar system with respect to it's parent planet.
    What do you mean, "with respect to the parent planet?" Ganymede is the largest moon in our solar system, not our own.


    Addendum... Is the below what you mean? If so, it's a bit of a false comparison, since Jupiter is so huge (1,320 Earths would fit inside of Jupiter).

    Ganymede Diameter: 5262 km
    Jupiter Diameter: 142984 km
    Size relative to "parent": 3.7%

    Our moon Diameter: 3475 km
    Earth Diameter: 12756 km
    Size relative to "parent": 27.2%
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  9. #8  
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    Yes, Inow, that is what I was talking about. Ox asked "Is our moon the largest in the solar system with respect to the size of its host planet?"

    Granted it isn't a fare comparison because Jupiter is so much larger, however it is a true statement.

    Jupiter would have to have a moon approximately 3 times the size of Earth to get a similar moon to planet ratio. Which as you said isn't really fair for Jupiter but it is still a true fact that the Earth's moon to parent planet ratio is the largest in our solar system.

    However there are smaller planets than Jupiter that still don't have moons to planet ratios as large are Earths.

    The Pluto-Charon system however might actually have a larger planet to moon ratio than Earth, but since we don't count Pluto as a planet any more, I don't believe that would count.
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  10. #9  
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    Quote Originally Posted by Haasum
    The Pluto-Charon system however might actually have a larger planet to moon ratio than Earth, but since we don't count Pluto as a planet any more, I don't believe that would count.
    Now... THAT, sir... is an excellent point. I had not even thought of that.
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    What I find strange about Pluto is whether it came from the Kuiper belt or was flung outwards by a near encounter with Jupiter (or Saturn), is that it is a double system, with Charon. Surely any violent movement early in it's career would have left it a single body system? Unless maybe the second incoming body was sufficient to knock it out of the plane of the solar system and yet low enough in power that Charon could not escape Pluto's gravity?
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  12. #11 Re: pluto 
    Universal Mind John Galt's Avatar
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    Quote Originally Posted by ox
    But what about the Giant Impact Theory where our moon was ejected from earth after a collision between the earth and an asteroid or meteor.
    A correction: it was not an asteroid or meteor, but a planet about the size of Mars.

    Quote Originally Posted by ox
    . .....I must admit however that the moon's large size makes this theory doubtful,
    No it doesn't. This remains the most favoured explanation for the Moon's origin. Increasingly focused computer modelling of the impact is able to explain the composition of the moon and the dynamic character of the Earth-Moon system.

    Quote Originally Posted by ox
    However, back to Pluto. If not an ancient moon, could it possibly have been a deep space body entering our solar system and getting caught in the sun's gravity?
    Well it could be. It could also be a giant holographic projection placed there by aliens with a sense of humour. Do you also think that Eris and Triton and Varuna and Makemake and Haumea and Sedna and Orcus and those other Pluto like bodies yet to be discovered, should all be considered ancient moons that have entered the system from outside? We have a perfectly sound explanation for the origin of Pluto. Why do you need to introduce a highly unlikely hypothesis, for which there is no obvious evidence?
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  13. #12  
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    Formation of Pluto can not be considered separately from the formation of the asteroid family Plutino. It is unrealistic that all Plutinos were earlier moons.
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