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

  1. #1
    Join Date
    Nov 2004

    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
    Join Date
    Jul 2005
    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
    Join Date
    Mar 2004
    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
    Join Date
    Sep 2020
    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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