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B Most detailed picture of Antares

  1. Aug 24, 2017 #1

    mfb

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    eso1726a.jpg
    From ESO

    An image of Antares, taken with the Very Large Telescope in interferometry mode. It is the most detailed picture of any star apart from the Sun. The star has 900 times the diameter of Sun and is (sort of) nearby at 550 light years distance, making it a great target for these observations. The star has an apparent diameter of 41 milliarcseconds, corresponding to the width of a human hair seen from 500 meters away.
     
  2. jcsd
  3. Aug 24, 2017 #2

    Borg

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    I saw this on a Space.com article yesterday. Pretty incredible that we can see such detail at that distance.
     
  4. Aug 27, 2017 #3
    Remarkable image, but the question in my mind is, what are we seeing? Are the bright areas zones of convective upwelling and the dark zones convective downturns? Or vice versa? Or something else. I have not had time to fully grasp the associated paper to determine if my suspicions are valid.

    If they are the surface expression of convective cells then they are very large and few in number. I therefore found this paper's prediction, from 1975, intriguing:
    "An attempt is made to estimate the sizes of the convective elements which dominate the brightness variations on the photospheres of red giants and supergiants. The data assembled permit the extreme hypothesis that these dominant convective elements are so large that only a modest number of them exists at any one time on the entire surface of such a star - in contrast with two million granules on the sun."
     
  5. Aug 27, 2017 #4
    Wow! Cool photo!
    Antares (Alpha Scorpii) is a red supergiant. I see it every night [twinkling reddish] west these days, early night hours, before it sets. It is also a double star. It's companion, Antares B, is much smaller and hard to see.

    With my small 60mm refracting telescope (and even bigger telescopes) I only see a bright twinkling reddish dot of course, when I look at Antares. But that picture in the OP is way beyond anything I've seen for a star from earth. I'm wondering how Alpha Centauri (nearest star system to earth [4.37 light years away]) would look like with similar telescope views?
    But it's a much smaller star [system*]! So no big luck:
    hubble_friday_09022016.jpg
    https://www.nasa.gov/image-feature/goddard/2016/hubbles-best-image-of-alpha-centauri-a-and-b/

    *Alpha Centauri is a binary star (A, B), orbited loosly by C (a small and faint red dwarf), the Proxima Centauri (nearest star to earth [4.24 light years]), way smaller than the other two, which are comparable to our Sun ...
     
  6. Aug 28, 2017 #5

    mfb

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    Antares has one of the largest angular diameters from Earth, and the VLT in interferometry mode has the best angular resolution available. The combination of both is needed to get such a picture. It is no surprise that you can't see details with hobby equipment.

    The Sun as exception, of course.
     
  7. Aug 28, 2017 #6
    Additionally the Alpha Centauri picture above is taken using HST regular cameras and not VLT in interferometry mode. Alpha Centari A has an angular size of 7 milliarcseconds (compared with 41 for Antares and 49 for Betelgeuse) so it too could be resolved using VST.
     
  8. Aug 28, 2017 #7

    mfb

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    If there are significant brightness variations there might be something visible, but I don't expect large-scale brightness variations for the Alpha Centauri stars.
     
  9. Aug 28, 2017 #8
    I don't expect any significant variations either since the Alpha Centauri stars should be living much more sedate lifes than a red super-giant but it is resolvable which was sort of the question asked (what would it look like using VST).
     
  10. Aug 28, 2017 #9

    mfb

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    Well, it has 1/6 the angular diameter of Antares, with some goodwill you can see something like 7 brighter/dimmer spots across its diameter "\"-direction, so I guess you can at least compare the brightness of different hemispheres.
     
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