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Will Pluto crash into Neptune?

  1. Oct 8, 2011 #1
    The orbit of Pluto crosses the orbit of Neptune because the eccentricity of Pluto is much greater than Neptune and the rest of the Planets. This causes Pluto to stray into the path of the orbital plane of Neptune. Using a present day model to calculate a happenning of more than 100 years is a travesty but Pluto will come within 150000km or 0.001au on three separate years:


    Someone please correct me if I am wrong. Any input would be appreciated!!
  2. jcsd
  3. Oct 8, 2011 #2
    While Pluto does cross Neptune's orbit as viewed perpendicular to the orbital plane, viewed parallel to the orbital plane it is tilted it over 8 AU above Neptune's Orbit. So while from an 'above' perspective, Pluto does cross Neptune's orbit and become closer to the sun, it's orbit is highly angled and so when it does cross Neptune's Orbit, it is actually about 8 AU above/below Neptune.

    There are also other reasons why this relationship is stable, and Wikipedia has a good overview of those:
  4. Oct 10, 2011 #3
    Hmm but our solar system does not spin like a flat disk - it's actually rotating AND moving through space - and all the planets paths are cork screws.
  5. Oct 27, 2011 #4


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    Although it is true that the solar system is moving through space, the entire system is moving roughly "together". So, planetary paths only look like corkscrews when viewed from outside the solar system. Viewed from a reference frame that is stationary relative to the sun, the orbits are elliptical. It does spin like a flat disk (well, almost flat). As already stated, Neptune and Pluto's orbits do not cross, when viewed three dimensionally.

    These two bodies have occupied these orbits for quite some time; long enough to have collided long ago if the relationship was not stable.
  6. Nov 1, 2011 #5
    I think Pluto's orbit is very eccentric and has a higher degree of orbit last I remember, relative to the other 8 planets.

    The orbital lines dont actually cross anywhere do they? Is 8 AU enough to make a difference in orbit? I would think very little if not at all..
  7. Nov 1, 2011 #6
    No, as LURCH said, were the orbits not stable, Pluto and Neptune would have collided long ago.
  8. Nov 1, 2011 #7


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    I don't think it is a 'travesty' to try and predict the future orbital motions of the solar system. The physics and the initial conditions are well enough understood that we can probably predict the orbits of the planets millions of years into the future, and there are multiple groups doing just that. They have found that Pluto's orbit appears to be stable for at least the next 10 million years, but beyond that the orbit becomes chaotic and we lose all predictive power. This link is a good place to start:

  9. Nov 1, 2011 #8

    D H

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    Where did you get these numbers?

    Pluto is locked in a 3:2 resonance with Neptune. Pluto never comes closer than 17 AU to Neptune. Pluto in fact comes closer to Uranus (to within about 11 AU) than it does to Neptune.

    I suggest you read the "Dynamics of Pluto" webpage at nineplanets.org, http://nineplanets.org/plutodyn.html The information and the graphics on this page are from the article "Pluto's Heliocentric Orbit" published in "Pluto and Charon" (Stern and Tholen, ed). Astronomy Abstract Service reference: http://adsabs.harvard.edu/abs/1997plch.book..127M. A pdf version of the article (unfortunately not the best quality) is at http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/32463/1/94-0204.pdf [Broken].
    Last edited by a moderator: May 5, 2017
  10. Nov 1, 2011 #9


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