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A KIC 8462852 (dipping again in March 2018)

  1. Sep 15, 2017 #261

    Drakkith

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    Probably. I don't think the interval between dips is short enough or regular enough to be explained by such a planet, which, according to the article, is a type of "hot Jupiter". These planets general have an orbital period of a few days and they cause predictable dips in the light curve instead of erratic dips.
     
  2. Sep 16, 2017 #262

    mfb

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    There is some periodic structure, but nothing a single planet could do. The dips observed by Kepler are way too deep for any sort of planet, and they also last too long and have a structure too complex for a planet.

    Multiple planets with ring systems are possible.
     
  3. Sep 18, 2017 #263

    stefan r

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    Alien fifth graders making a mega-structure does not have any evidence that I can find. :alien: Would be a sub category in "aliens made it". A megastructure made out of polystyrene seams as plausible as aluminum, steel, shell (silica, calcium carbonate), or spider silk. Any would still be a remarkable find.

    A polystyrene foam with density 0.05 g/cm2 and earth radius would collapse into high density polystyrene. High temperatures and pressure would then modify the chemistry. I believe a Jupiter mass planet made out of an equal parts mix of hydrogen and carbon would be denser than Jupiter. Adding more mass does not increase the volume. Brown dwarfs are close to Jupiter's volume. A hollow shell with 20X Jupiter's surface might not collapse. It is hard to explain how that would come to exist.

    Astronomers have found low density planets with radii larger than Jupiter. The article referred to KELT 11b. Hot Jupiter planets orbit close to stars and are hot. The high temperatures help explain the low densities. A 760 day orbit would not add much more heat than earth gets from the sun (per square meter).

    The thing around KIC 8468252 would have to have 1/5th KIC 8468252's cross section in order to block enough light. A hot surface radiates infra-red radiation. When a hot Jupiter passes in front of a star the infra-red should drop less than the measured visible light. When a hot Jupiter passes behind a star the measured infra-red drops but visible light will measure normal for that star.

    As a hot Jupiter sphere revolves the visible light should gradually change as the light reflecting off the surface waxes and wanes. Like full moon to new moon phase cycles. The reflected light also eclipses when the planet passes behind the star. The object around KIC 8468252 could be extremely dark and/or not a sphere.
     
  4. Sep 18, 2017 #264
    Hot Jupiter's also make the star itself wobble which there is no evidence for there. Whatever is passing in front of the star seems to have negligible mass.
     
  5. Sep 18, 2017 #265

    stefan r

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    This article claims they only measured within 400 m/s radial velocity. In their model they have a planet with orbital period ~12 years and trojans making the 2 year events. They calculate total mass less than 130 Jupiters.

    The ESO has HARPS installed on a telescope and they claim 1 m/s velocity measurements. They built one for the northern hemisphere but measurements of KIC 8462852 did not come up in a google search. I would not call 1/4th Jupiter mass "negligible".
     
  6. Sep 23, 2017 #266
    A conglomeration of dark matter?
     
  7. Sep 23, 2017 #267

    Drakkith

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    Unlikely. The dark matter model that best fits the available evidence points towards dark matter which doesn't conglomerate.
     
  8. Sep 23, 2017 #268

    stefan r

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    "Dark matter" is a single concept. Does not mean the same thing as "matter which is dark". In order to be "dark matter" it does not emit, adsorb, or reflect light.
     
  9. Oct 26, 2017 #269
  10. Oct 26, 2017 #270
    Yeah, the dust "proof" settles everything.

    Except the gradual, century long dimming.
    Or the periodic brightening of the star.
    Or why the dust hasn't been pulled into the star if it's in the system.
    Or how dust that's far away but in between us and it could have such dramatic occlusion.

    So I'm just SURE this hypothesis won't end up like the past 27 hypotheses.
    Yeah.
     
  11. Oct 26, 2017 #271

    mfb

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    Do you have a reference that dust cannot explain these?
     
  12. Oct 27, 2017 #272

    stefan r

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    Spitzer measured infra-red at 4.5μm . If a black body at 370 degrees C it should radiate 4.5μm radiation. Is there a way to distinguish between a filter that blocks only UV and a filter that blocks some of everything and also emits lower frequencies? The temperature on Mercury's equator rises over 400C.
     
  13. Mar 19, 2018 #273

    mfb

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    During January and February, the star is too close to the Sun for observations. Measurements resumed two weeks ago, and since March 16 the star shows another dip. Currently 4% below the baseline, the deepest dip seen since the end of Kepler observations.

    Image source and more information: tldr: DIPPING!!!

    KIC_mar18.png
     
  14. Mar 27, 2018 #274

    mfb

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  15. Mar 27, 2018 #275
    Could it be that the visible star has two or more very large but non-luminous brown dwarf objects associated in that system?
     
  16. Mar 27, 2018 #276

    stefan r

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    How are they calculating the error?
    How are they determining normal?

    A brown dwarf has close to the same radius as Jupiter. A 4% dip requires more like 7 Jupiter sized objects.

    Brown dwarf stars close to KIC8462852 would show some Doppler shift. There could be lots of cold brown dwarfs in many places.
     
  17. Mar 27, 2018 #277
    It doesn't come in gradually, like a body transiting. It dims suddenly. And randomly.?
     
  18. Mar 28, 2018 #278

    mfb

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    I don't know, see the linked web page for details. Kepler just normalized to the flux outside the dips, but the star seems to have a non-constant apparent magnitude outside the dips as well.
    Compared to planet transits the dips have quite long slopes. Jupiter moves by 1 diameter in its orbit every 1.5 hours, but the dips start and end over 1-3 days.
     
  19. Mar 29, 2018 #279

    JMz

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    Saturn's rings have a radius of 120,000 km but are only partially opaque, whereas the Sun has a radius > 400,000 km. So at most, the rings would absorb about 8% if they were opaque and properly oriented wrt the star and properly oriented wrt us.

    Note that there is no direction in which a star could see Saturn's rings oriented that way wrt to the Sun.

    BTW, if Saturn were so oriented, then every time it passed between the Sun and that star, it would present the same face. That star would not see only the planet sometimes, and planet+rings other times.
     
  20. Mar 29, 2018 #280

    Vanadium 50

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    Why?
     
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