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Thread: How to tell the difference between a merely hyperbolic comet and an interstellar one?

  1. #1
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    Nov 2004
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    How to tell the difference between a merely hyperbolic comet and an interstellar one?

    I've always been puzzled by that, since a hyperbolic trajectory would imply an interstellar origin, no?
    "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.

  2. #2
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    Objects perturbed out of the Oort can also have hyperbolic orbits--a very slight perturbation at such an extreme distance can convert a near-circular orbit to a hyperbolic orbit that will make a single pass through the inner solar system and then depart into interstellar space.
    The difference is essentially a statistical one, based on an analysis of the orbit:

    Hyperbolic Orbits in the Solar System: Interstellar Origin or Perturbed Oort Cloud Comets?

    Grant Hutchison

  3. #3
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    There is another more subtle difference to watch for. Broadly put, the masses of the planets affect the orbit when outside each of them (in a time-averaged sense). It is possible for a very long-period comet, which is just barely bound to the Solar System, to have a formal eccentricity slightly greater than unity when observed only near the Sun. (That is, Kepler's third law breaks down for distributed masses, at a level which matters for comets which are so weakly bound to the whole system, so the entire orbit is not exactly a single conic section). Much of the initial excitement over 'Oumuamua was that its eccentricity was very much larger than either of these explanations can give.

  4. #4
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    Sep 2020
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    It seems to me that this can only be done by calculating the trajectory in order to understand if the object was blown away. As far as I understand, comets, from whatever cloud they are thrown out, have a dry structure and chemical composition. It turns out that they are distinguished only by the place of their release outside the cloud? Correct me if I misunderstood, I'm new to this question.

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