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Sedna's Orbit

  1. Jul 13, 2010 #1
    What does most evidence point to regarding the reasons for Sedna's looong orbit? I think it highly unlikely that the Sun's gravitation can keep it in place.
  2. jcsd
  3. Jul 13, 2010 #2
    Why do you believe that, when the Sun is more than enough to constrain long-period comets, with orbits that extend beyond Sedna's? I would add, it has been argued that it is "in place" as an object in the Oort Cloud, and not a scattered disk object.

    Here are the various hypotheses on wikipedia which seem to cover the spectrum of believable reasons:

    Last edited: Jul 13, 2010
  4. Jul 13, 2010 #3
    No, I mean, how do you justify the elongation? Considering the average spacing between the orbits of the other planets, Sedna's orbit canNOT be explained by just our Sun.

    The Wiki entry does explain the origins of the orbit, but other than the Nemesis hypothesis, is there a valid ground for the continued orbit of Sedna around the Sun, unless you consider it a part of the Oort cloud?
  5. Jul 13, 2010 #4
    I don't know, and I don't think anyone does. I don't believe this necessitates the existence of Nemesis. All of the ones I could think of, and one more are in the wikipedia article. There simply is no answer to your question, only the conundrum itself.
  6. Jul 13, 2010 #5


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    Staff: Mentor

    The way you word a lot of that doesn't make much sense. An orbit is an orbit, highly elongated or not. It doesn't require another object and there is no reason why it wouldn't continue to orbit unless it interacts with another body.
  7. Jul 13, 2010 #6
    That interaction could have been a long time ago, and the effects are being seen over time, right? The interaction established an orbit (which evolves over time), but isn't required on a constant basis.
  8. Jul 14, 2010 #7


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    Science Advisor

    Sure it can! Gravity is an infinite-range force, so if there was no other matter out there beyond our solar system (and no cosmological constant), there could, in principle, be objects with orbits around our Sun that were quadrillions of light years in length. It would obviously take an absurdly long time for such an orbit to occur, but there is no problem with it happening.

    So the real thing that limits the size of orbits isn't gravity, but instead other stuff out there that would disturb their orbits. But the nearest star is around 3 light years away, which is so vastly further than Sedna's orbit isn't even funny. So until Sedna passes nearby some other object within our own solar system, it'll just keep orbiting the Sun in its current orbit.
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