EHT First image of Black Hole

Discussion in 'Astronomy, Exobiology, & Cosmology' started by sweetpea, Apr 10, 2019.

  1. sweetpea Valued Senior Member

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    Well, would you believe it!
    Details have been published today in Astrophysical Journal Letters.
    https://iopscience.iop.org/issue/2041-8205/875/1
    https://iopscience.iop.org/article/10.3847/2041-8213/ab0ec7/meta

    This from BBC
    https://www.bbc.co.uk/news/science-environment-47873592
     
    Last edited: Apr 10, 2019
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  3. Janus58 Valued Senior Member

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    Just one caveat. The BBC article says "was photographed by a network of eight telescopes across the world". To prevent any misconceptions: these were radio telescopes receiving EMR outside of the visible spectrum. So the image is a visual representation of the "radio" image they picked up, and not a direct photograph made from visible light.
     
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  5. exchemist Valued Senior Member

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    One question: if this black hole is surrounded by gas emitting radiation, as they say, how is it we are being shown a picture which has a dark patch in the centre?
     
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  7. sweetpea Valued Senior Member

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    I can't really answer that, but wondered, if there's 'light' all over the black hole 'globe' but more 'light' from the plane of the accretion disk because its hotter??
    Of course all this global 'light' is outside the horizon.
    Begging the question...Are we just lucky to be looking down from above a pole? I'm guessing of course. Come back Janus58
     
    Last edited: Apr 10, 2019
  8. exchemist Valued Senior Member

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    Or perhaps we see a greater thickness of light-emitting gas, edge on, at the sides than we do directly in front, and so it seems more intense at the sides. That would be my best guess but I am not confident of it. Janus may help us out.
     
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  9. James R Just this guy, you know? Staff Member

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    I think we're probably looking at it side on, more or less, because the brighter gas at the top of the image is brighter because it is moving towards us, whereas the gas below is moving away. The accretion disc might be thin (edit: that might not work - depends on the diameter the hole. This one is a big one, containing several billion solar masses).

    On the other hand, the thing emits a relativistic jet that can be seen in part. It is not aimed at us, so we're not looking down on a pole of the hole. But nor is the jet at 90 degrees to us, since we only see it on one side of the hole. The reason we don't see the other side is that the "jet" on that side is Doppler shifted as it moves away from us, approximately.

    Maybe I ought to read the actual paper or something. Sounds like work, though.
     
  10. exchemist Valued Senior Member

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    ....or wait for Janus to return and tell us. I'm sure he will have read it.
     
  11. Janus58 Valued Senior Member

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    This is from the paper:

    Please Register or Log in to view the hidden image!


    Figure 5. Illustration of the effect of black hole and disk angular momentum on ring asymmetry. The asymmetry is produced primarily by Doppler beaming: the bright region corresponds to the approaching side. In GRMHD models that fit the data comparatively well, the asymmetry arises in emission generated in the funnel wall. The sense of rotation of both the jet and funnel wall are controlled by the black hole spin. If the black hole spin axis is aligned with the large-scale jet, which points to the right, then the asymmetry implies that the black hole spin is pointing away from Earth (rotation of the black hole is clockwise as viewed from Earth). The blue ribbon arrow shows the sense of disk rotation, and the black ribbon arrow shows black hole spin. Inclination i is defined as the angle between the disk angular momentum vector and the line of sight.

    There was also this reference to the orientation of the BH:
    So it does appear that we are looking nearly "straight down" at the BH.
     
  12. sweetpea Valued Senior Member

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    Thank you Janus58.
    ---------------------------
    I know the it's bad form to say ''here's a clip'' and not give any comment, but the following clip explains the different types of views of black holes that are possible.
    For instance, that black patch in the centre is not all black hole. Also, if this was an edge-on accretion disk view, then there would be a bright ''line'' across the black hole. Points 5:00 and 7:06 in the clip are good. Thanks paddo. I don't think this clip is a waste of time. But, aho, people can ignore this post if they like.

    https://www.reddit.com/r/space/comments/bb7q2o/how_to_understand_the_image_of_a_black_hole/
     
  13. paddoboy Valued Senior Member

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    A belated no probs!!!

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    Here is some more info of this incredible successful endeavour with regards to size.....

    https://imgs.xkcd.com/comics/m87_black_hole_size_comparison.png

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    We are truly living in a great age of astronomical discoveries and scientific verifications of BH's and GR....
     

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