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Thread: Planet 9 a planet?

  1. #1
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    Planet 9 a planet?

    If Planet 9 is found would we be able to call it a planet under the rules that disqualified Pluto?
    See: 'The God Kit' -- 'The Brigadier And The Pit' -- Carl N Graham -- Sci-fi blog: The Alien Reporter

  2. #2
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    Quote Originally Posted by PetTastic View Post
    If Planet 9 is found would we be able to call it a planet under the rules that disqualified Pluto?
    I doubt it because the rule now is that it has to clear its orbit, and AFAIK any new planet we are likely to discover will be in the Kuiper belt, and so has not cleared its orbit. But I could be wrong on that.
    As above, so below

  3. #3
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    This just shows that there are bugs in the classification scheme when we go outside the domain in which it was invented. The possible existence of Planet 9 is inferred from perturbations attributed to it. It is a massive body that can throw its weight around and shepherd several TNO orbits into orientations we would not expect from random action. If that is not a planet, I don't know what is.

  4. #4
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    The rules about clearing the orbit aren't asking for 100% clearance. There is a mass ratio between the object and the remaining material, and something at 5 Earth Masses would probably qualify as a planet even in the main Kuiper Belt, but in the outer Kuiper Belt, the ratio is going to be even better for declaring it a planet. ... that being said, once we know details about thousands (or more) exoplanets, I expect the term "planet" to be loosely used as a description, with awareness that there will be objects in the gray area of the definition, and if you want to talk about a specific object you will refer to it by name or catalog id.
    Forming opinions as we speak

  5. #5
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    There is an interesting paper by Jean-Luc Margot, "A QUANTITATIVE CRITERION FOR DEFINING PLANETS" that may prove useful in tweaking the gray area for planethood for solar and extrasolar systems. It demonstrates that a 6 Earth-mass object would have the capability of clearing its orbit (given enough time) if it's within a little less than 2000AU. Assuming 600 AU for the possible Planet 9, it would have traveled about 47,000 orbits in 4 billion years, assuming a circular orbit.
    We know time flies, we just can't see its wings.

  6. #6
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    How about finding it first, and then worrying about what to call it?
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