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Thread: Up to 22% Dips Detected in Starlight 1,500 LY Away

  1. #751
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    And now my real question.

    Does Tabby's Star's oddity orbit in a different plane than the Tabby's Star's equator?
    Time wasted having fun is not time wasted - Lennon
    (John, not the other one.)

  2. #752
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    I may be wrong, but I don't think we know what the equator of the star is.
    As above, so below

  3. #753
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    Quote Originally Posted by Jens View Post
    I may be wrong, but I don't think we know what the equator of the star is.
    they can usually tell from the red-shift and blue-shift, of the sides of the star, if it is rotating, I think...not sure.
    Formerly Frog march..............

  4. #754
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    Tabby's Star is not resolved. The image of it is, in effect, a single pixel. There is no opportunity to compare the relative motion of one side, to the other. Regular minor fluctuations in brightness are inferred to give a rotation period of ~ 0.87 days. The inclination of the star's equator is not known.
    Last edited by Ross 54; 2017-Jul-31 at 01:01 AM.

  5. #755
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    can they tell how fast it is revolving, despite not being able to tell which way? I'm not sure, but maybe they could tell by how far any light is blue-shifted, and how much some is red shifted...
    Formerly Frog march..............

  6. #756
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    Quote Originally Posted by Frog march View Post
    can they tell how fast it is revolving, despite not being able to tell which way? I'm not sure, but maybe they could tell by how far any light is blue-shifted, and how much some is red shifted...
    As Ross 54 said, as we are only seeing one pixel essentially, it will be the average of the red shift and blue shift. So we can't tell. Remember, it's 1500 light years away.
    As above, so below

  7. #757
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    Quote Originally Posted by Jens View Post
    As Ross 54 said, as we are only seeing one pixel essentially, it will be the average of the red shift and blue shift. So we can't tell. Remember, it's 1500 light years away.
    yes, I just wondered if its spectrum had a sort of bell curve. I wondered whether they could tell how fast its surface was travelling from the shape of a bell curve.
    found this:
    Rotational Motion

    Even though we can still only resolve most stars as point sources they are in fact large, roughly spherical balls of hot gas and plasma. Stars rotate, that is they spin on their axis. The Sun's sidereal rotational period is about 26 days on the solar equator and possibly up to 36 days at the poles. The different rates is due to the fact that it is not a solid sphere and the gas and plasma can rotate at different speeds.
    If we obtain a spectrum from a distant star that is rotating in the same plane as us then the light gathered is a combination of light from across the disc of the star. As part of the star appears to rotate towards us its light will be blueshifted. The light from the part of the star rotating away from us will be redshifted. The section in the middle of the disc that is moving tangentially to us will not exhibit Doppler-shift.
    What effect will this have on the star's spectrum?
    The net effect is that the star's spectral lines will appear smeared out. This broadening of lines can be distinguished from the effects of pressure broadening due to stellar pressure discussed in the next section. The beauty of rotational broadening is that it can be used to measure the rotation rate of stars. As with translational velocity the alignment of the plane of rotation of the star with Earth is a factor and must be calculated from the spectrum.
    http://www.atnf.csiro.au/outreach/ed...ctra_info.html
    Formerly Frog march..............

  8. #758
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    Quote Originally Posted by BigDon View Post
    Dang Tom, some people on this board have absolutely no color to them at all. (In reference to color commentary vs. technical commentary.)

    How sad for them.

    I suppose if you said something like your wife was going to kill you for denting the car, CJSF and others would call 911 for you.

    Cj, before you get tic'ed about what's obviously a peeve with you, Tom did state in the very same sentence he's received a B.S. in astronomy, ergo, he knows damn well how science "really works".
    What? Obvious to whom?

    CJSF

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  9. #759
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    Yes, for rotation of the star. Now what?

    Wikipedia: KIC 8462852

    Rotation 0.87970.0001 days
    Rotational velocity (v sin i) 844 km/s
    0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
    ATM is so 20th Century.

  10. #760
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    The fact that they can measure a rotation velocity presumably means the star is not observed pole-on from here ?

    Could the data be used to constrain our viewing angle?

    Next question, are we not due some conclusion on the supposed orbital periodicity by now? I have a vague memory that we should be seeing the same material coming round again by end July this year.

  11. #761
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    Quote Originally Posted by BigDon View Post
    Dang Tom, some people on this board have absolutely no color to them at all. (In reference to color commentary vs. technical commentary.)

    How sad for them.

    I suppose if you said something like your wife was going to kill you for denting the car, CJSF and others would call 911 for you.

    Cj, before you get tic'ed about what's obviously a peeve with you, Tom did state in the very same sentence he's received a B.S. in astronomy, ergo, he knows damn well how science "really works".
    BigDon

    A request for a summary of a link is perfectly reasonable. Calling out other members is not at all reasonable and you should know better. And if you did have a concern about some post, you know to report it. This will earn an infraction.
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