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Thread: new method for finding another planet?

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    Default new method for finding another planet?



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    Default Re: new method for finding another planet?

    Early this year, a study was published that demonstrated that the clustered orbits of distant Kuiper belt objects (and several other features of our solar system) can be explained by the gravitational tug of a yet-undiscovered planet. This hypothetical Planet Nine is predicted to be a giant planet similar to Neptune or Uranus, with a mass of more than ~10 Earth masses, currently orbiting ~700 AU away.
    At 700 au, would this hypothetical 'planet' be gravitationally bound to the sun? I am remembering some of the wide double star pairs I looked into as part of my project. At that separation, the stars didn't really orbit, instead they showed common proper motion characterized by a sort of fishtail movement.

    Also, been a long while since I checked, but wasn't Pluto originally predicted to be far more massive than proved to be the case?
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    Default Re: new method for finding another planet?

    Quote Originally Posted by ThinkerX View Post
    At 700 au, would this hypothetical 'planet' be gravitationally bound to the sun? I am remembering some of the wide double star pairs I looked into as part of my project. At that separation, the stars didn't really orbit, instead they showed common proper motion characterized by a sort of fishtail movement.
    That's what a widely separated orbit looks like. Gravitation does not have a cut off. The Oort cloud is bound and is much larger. A distant observer would see Earth as having a common proper motion with the Sun and having something like a fishtail movement.

    Also, been a long while since I checked, but wasn't Pluto originally predicted to be far more massive than proved to be the case?
    Yes and the basis for that mass prediction (anomalies in Neptune's orbit) has been correctly attributed elsewhere. Finding Pluto was a lucky accident. Finding Neptune wasn't, though.
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    Default Re: new method for finding another planet?

    Hmm...

    The double star info for my project included a number of professionally calculated orbits. Two or three gave...fair guesses (Grade 5) orbits for binaries with separations that worked out to 100 au, give or take, and orbital period on the order of tens of thousands of years. So, with that as a guide...

    a planet 700 au out would have an orbital period on the order of a couple hundred thousand years, maybe?

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    Default Re: new method for finding another planet?

    Kepler tells you how to calculate it.
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    Default Re: new method for finding another planet?

    When Mike Brown taught the Astronomy MOOC just a year ago, he went so far to say that there is no planet 9. So, I was surprised to hear him say that he changed his mind, on CBC radio interview a few months ago. With all the newly discovered minor planets and other objects revolving around our Sun, of course it boils down to a less interesting question of semantics. We're talking about a celestial body that is (presently) so far out there that I don't think it belongs in the group of planets we have defined to date. I suppose if it had such an elliptical orbit that it will come closer in future centuries, it would be worth reassessing. Even so, a strange orbit was one of the reasons Pluto was reclassified. For now it's an intriguing observation that sparks curiosity and imagination. Successful scientists have the panache to energize discussions like this one.
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    Default Re: new method for finding another planet?

    The problem with defining an object like a planet by its orbital characteristics is going to be a never ending one. The dynamics of planetary systems are unstable. Planets exist with no orbits.

    https://en.wikipedia.org/wiki/Rogue_planet

    A good definition aims at being always usable and applicable. A definition that is subject to the chaos of dynamics is not a good one. Does a planet cease to be a planet because it was ejected from a system? Stars that reach escape velocity and leave the galaxy do not cease to be stars. Why should ejected planets cease to be planets.

    I will always oppose reclassifying objects on the basis of mutable orbital history. If you want a good example of a bad definition take the IAU's current definition of 'planet'. It (as I have argued above) is unsatisfactory as a definition with pretensions of being scientific. It is simply the projection of an emotional desire to keep the number of planets artificially low.

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    Default Re: new method for finding another planet?

    PS The very fact that folks have to "change their mind" about whether an object is a planet or not is a tacit admission that the definition is inadequate and ad hoc.

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    Default Re: new method for finding another planet?

    Quote Originally Posted by not_Fritz_Argelander View Post
    Finding Pluto was a lucky accident. Finding Neptune wasn't, though.
    Oh please it was at least a degree away from its predicted position
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    Default Re: new method for finding another planet?

    Quote Originally Posted by MG1692 View Post
    Oh please it was at least a degree away from its predicted position
    Neptune was a degree away from the position predicted by LeVerrier but it was twelve degrees away from the position Adams predicted. LeVerrier just did the math better and achieving one degree accuracy with pencil and paper math was quite good. The uncertainty was more than a degree so the prediction counts as a success. (Before complaining about accuracy one must always consider uncertainties.)

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