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    • CommentAuthorAsterix
    • CommentTimeAug 21st 2021
     
    We could send Elon on a SpaceX rocket to investigate...
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      CommentAuthorjohnq
    • CommentTimeAug 21st 2021
     
    enroute

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      CommentAuthorTrim
    • CommentTimeAug 28th 2021
     
    Lets hope all goes well.

    This way up: James Webb Space Telescope gets ready for shipment after final tests.

    https://www.theregister.com/2021/08/27/jwst_shipment/
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      CommentAuthorAngus
    • CommentTimeSep 2nd 2021
     
    Amazing to detect a 1km size object at intergalactic distance.
  2.  
    JMG
    https://www.youtube.com/watch?v=u4mRsT9emtI
    appears on camera for the first time (of which I'm aware).

    FWIW, totally matches my prediction (middle aged, ugly, pony tail).
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      CommentAuthorAngus
    • CommentTimeOct 18th 2021
     
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      CommentAuthorAngus
    • CommentTimeOct 29th 2021
     
    The spectroscopic doppler shift method for planet-finding should be independent of stellar distance. I wonder if anyone ever tried it on ihe sun to see if the algorithms give eight planets and Pluto.
  3.  
    Good question. But we are so close that astrometry could probably suffice.
    • CommentAuthorenginerd
    • CommentTimeOct 29th 2021
     
    Now I remember one of the reasons I liked this place for so long. Stuff comes up that makes me want to learn something. I have been reading up on spectroscopic doppler-shift planet finding (don't know that I ever encountered the notion before seeing it here). It amazes me that instruments are sensitive enough to measure such small velocity changes at such distance.

    I don't know that much about complex orbital mechanics, but I don't think we could resolve the match from the net velocity change, sufficient to describe the participation of multiple planets. It seems to me that even two planets would give you a concatenated velocity change, and no way to ascribe it to two different contributers. Certain 3 bodies and above represent a tricky trick.

    Also, earth-size planets seem to be still on the borderline of detectability. Pluto, planet or no, would still be a no go.

    Now, if someone will correct me on any of this, I will learn even more.
  4.  
    The trick is to Fourier transform the data with timescales measured in years. The characteristic orbital frequencies should then magically pop out.
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      CommentAuthorAngus
    • CommentTimeOct 29th 2021
     
    It does seem a difficult way to detect planets but in fact most of the early detections used this method.
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      CommentAuthorAngus
    • CommentTimeNov 1st 2021
     
    Bummer. No aurora here. I miss Churchill.
    • CommentAuthorAsterix
    • CommentTimeNov 2nd 2021 edited
     
  5.  
    https://scitechdaily.com/black-holes-may-gain-mass-from-the-expansion-of-the-universe-itself/

    There is such a thing as a free lunch where cosmological expansion is concerned. Each newly created volume of spacetime contains the same density of dark energy, and thus total universal energy grows apace. Since energy is mass equivalent, black holes should grow over cosmological time, which may explain the unexpectedly large BH masses seen by LIGO.

    However, it does perhaps also say something about what lies behind the event horizon, which only theory can describe. If this "cosmological coupling" idea is right, the spacetime inside the horizon is not so different from that outside it - despite the roles of space and time being theoretically swapped behind the event horizon, the cosmological constant still holds sway there.
    • CommentAuthorkorkskrew
    • CommentTimeNov 8th 2021 edited
     
    I guess the implication is that the mass lost to Hawking radiation is trivial compared to mass gained from expansion.

    The result was not only more massive black holes when they merged, but also many more mergers. When the researchers compared the LIGO—Virgo data to their predictions, they agreed reasonably well.

    I wonder how close "reasonably well" is to observations.
  6.  
    Yup - Hawking radiation for BHs of those sizes results in minuscule losses of mass. Indeed, the effective temperature of such BHs (again per Hawking's maths) is so low that they continually ingest radiation from the CMB - even at its present value of a few degrees Kelvin, and assuredly in the past when it appeared hotter.
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      CommentAuthorAngus
    • CommentTimeNov 8th 2021
     
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.


    Mark Twain, Life on the Mississippi
  7.  
    Written by a man who garnered "wholesale returns" from pure fiction.
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      CommentAuthorAngus
    • CommentTimeNov 8th 2021
     
    There you go!