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  •  If (1+ / 0-)
    Recommended by:
    Clem Yeobright

    the exoplanet orbits its star outside the plane of that star's equator, no matter how far out of the plane it may be, and still crosses in front of the star, yes, Kepler would potentially be able to detect the transit just like any other. In fact, my guess is we would simply infer that's where the plane of the star's equator was, becuase I don't think there's  any other way to tell with present technology anyway, and our theories and observations of existing protoplanetary disks, are disks, precisely because they accrue in a plane at right angles to the star's spin axis. It's an interesting side question as to how much a star's obliquity can change over time afterward. Just off the top of my head, my guess would be the larger the total mass of orbiting planets, the more 'locked in' a star would be to a smaller range of obliquity, but that math sounds fiendish to work out in detail.

    Read UTI, your free thought forum

    by DarkSyde on Sun Mar 08, 2009 at 07:03:34 AM PDT

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    •  one can tell whether (2+ / 0-)
      Recommended by:
      DarkSyde, Clem Yeobright

      an exoplanet orbits in a plane that is
      inclined to the equator of the star if the exoplanet also transits the star. This is
      called the Rossiter-McLaughlin effect and Greg Laughlin explains this nicely at
      oklo.org with respect to weird exoplanet around HD 80606

      H.L. Mencken: "A nation of sheep begets a government of wolves"

      by igneous on Sun Mar 08, 2009 at 07:36:52 AM PDT

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      •  "Equator of the star" (0+ / 0-)

        You are referring, I think, to the equator from our (Kepler's) perspective, NOT the equator defined by the rotation of the body, right?

        I'm still disoriented (can't find that damned East - it was here a minute ago, dammit!)

        1. Is the (apparent) brightness of a star distributed evenly across the disk or does the radiation proceed from within the star and is it therefore directional, so that an area near the (apparent) pole contributes less than does an equal area on the (apparent) equator to the light Kepler captures?
        1. Does a planet with a particular period whose orbit is - from our perspective - offset spend less time in its (apparent) transit than one with the same period that appears to follow the equator? I have to guess yes, since a planet offset by 90 degrees from us will appear to transit not at all, in zero time, one might say, and zero is a quite different value than any other.... [Never mind, I think I've resolved this one.]
        1. Does the effect you describe relate to the relationship of the transit time to the period?

        Thanks!

        Ignorance isn't exactly bliss but some things are better known when they are unknown to start with and pieced together on the way. - WineRev

        by Clem Yeobright on Sun Mar 08, 2009 at 08:53:48 AM PDT

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        •  How does this work? (0+ / 0-)

          An exoplanet (as an inner planet in our system) spends its time - from our perspective - in three states: occluding the star, occluded by the star, and neither occluding nor occluded. Mercury spends much less time in the third state than does Venus, because of Mercury's closer orbit.

          So the key to size and mass would be to determine how much time is spent in each state, and multiple observations permit the estimate of orbit size, no?

          Ignorance isn't exactly bliss but some things are better known when they are unknown to start with and pieced together on the way. - WineRev

          by Clem Yeobright on Sun Mar 08, 2009 at 09:04:53 AM PDT

          [ Parent ]

      •  If (1+ / 0-)
        Recommended by:
        Clem Yeobright

        a star did indeed roll its spin axis significanty after a planet's accretion, might the tidal effects then induced account for orbital migration inferred for some hot jupiters orbting their sun well inside the relative orbit of mercury?

        Read UTI, your free thought forum

        by DarkSyde on Sun Mar 08, 2009 at 08:59:16 AM PDT

        [ Parent ]

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