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Thread: First image of a black hole on April 10, 2019

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    First image of a black hole on April 10, 2019

    So they will present the first image of a black hole tomorrow morning apparently:
    https://phys.org/news/2019-04-black-...-darkness.html

    If I read correctly the article, all they have to do is measure the width of the black hole rings to confirm or refute the singularity predicted by GR, am I correct?


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    Last edited by slang; 2019-Apr-10 at 02:44 PM. Reason: title fixed

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    Quote Originally Posted by philippeb8 View Post
    So they will present the first image of a black hole tomorrow morning apparently:
    https://phys.org/news/2019-04-black-...-darkness.html



    If I read correctly the article, all they have to do is measure the width of the black hole rings to confirm or refute the singularity predicted by GR, am I correct?
    I think it would be better to say the evidence from the radio telescopes could be consistent or inconsistent with GR theory.

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    Quote Originally Posted by Van Rijn View Post
    I think it would be better to say the evidence from the radio telescopes could be consistent or inconsistent with GR.
    Sorry I do not understand.


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    Well, I wouldn’t call it an image of a black hole (and the article does sort of clarify that) and what is always at issue is consistency of evidence with theory. If evidence were inconsistent then they would have to determine the reason, which could be observational or might suggest new physics.

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    Quote Originally Posted by Van Rijn View Post
    Well, I wouldn’t call it an image of a black hole (and the article does sort of clarify that) and what is always at issue is consistency of evidence with theory. If evidence were inconsistent then they would have to determine the reason, which could be observational or might suggest new physics.
    Ok. And they could determine this with a single picture only?


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    XKCD covered this recently, the mischievous imps.

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

    Seriously, I had a similar problem (as referred to by XKCD ) after capturing my avatar image. As soon as I captured this image the 'Save As' box destroyed the developing feedback loop image. After this stage the black hole (made by my finger) would normally expand the circle into a full blown ring with many small waves running around the inside in one direction and similar running the opposite way on the outside.
    Last edited by LaurieAG; 2019-Apr-10 at 06:01 AM.

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    I gather the actual black bit will look very small....a pixel across? Not much to measure...
    ................................

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    Ok, if it doesn’t have a “ring shaped shadow” then GR is wrong:




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    Quote Originally Posted by philippeb8 View Post
    So they will present the first image of a black hole tomorrow morning apparently:
    https://phys.org/news/2019-04-black-...-darkness.html

    If I read correctly the article, all they have to do is measure the width of the black hole rings to confirm or refute the singularity predicted by GR, am I correct?
    The singularity is inside the event horizon and so could not be observed. Also, it is not a "thing"; it doesn't exist, it is just a failure of the mathematics. If it did exist, it would be zero size and therefore not visible.

    They will be measuring the diameter of the event horizon to see if it is consistent with the predictions of GR. I doubt this single measurement would be enough to refute GR.

    Here is an article that describes what they will be measuring: https://blackholecam.org/research/bhshadow/

    "The ultimate goal of BH shadow studies is to determine the theory of gravity that best describes the observations." (https://blackholecam.org/research/bhshadow/spacetimes/)
    Last edited by Strange; 2019-Apr-10 at 10:13 AM.

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    Quote Originally Posted by philippeb8 View Post
    Ok, if it doesn’t have a “ring shaped shadow” then GR is wrong:
    Even if the measurements do not come out as predicted, I don't think that based just on that suddenly everyone is going to announce "OH, GR is completely wrong! Scrap that!". There is just too much evidence in support of GR. I suspect there would first be an evaluation of what might be wrong with the measurements, and then with the predictions of what those measurements should be. If all of that holds up, I suspect there would be a push for further measurements, and then a look at modifications to GR.

    I also suspect a lot of people are expecting an image like a movie image of a black hole, and it isn't going to be anything like that.
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    Quote Originally Posted by Swift View Post
    I also suspect a lot of people are expecting an image like a movie image of a black hole, and it isn't going to be anything like that.
    A few black pixels, I suspect!

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    I was just watching the press conference and they showed the image, and it looked a lot like the image Strange linked to above (LINK), though without the fine lines in the bright region.

    The gentleman also said it was completely consistent with the predictions of GR. Sorry ATMers.

    Here is the image off of NSF's Twitter feed.
    Last edited by Swift; 2019-Apr-10 at 01:18 PM. Reason: added the image
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    And here it is. Impressive!

    Edit to add: Here's a link to the image itself, in case they don't have it on their main page forever (although that seems unlikely, actually).
    Last edited by Grey; 2019-Apr-10 at 01:19 PM.
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    Quote Originally Posted by Swift View Post
    I was just watching the press conference and they showed the image, and it looked a lot like the image Strange linked to above (LINK), though without the fine lines in the bright region.

    The gentleman also said it was completely consistent with the predictions of GR. Sorry ATMers.
    Oh that’s fine. We lost a battle but not the war


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    Quote Originally Posted by Grey View Post
    And here it is. Impressive!

    Edit to add: Here's a link to the image itself, in case they don't have it on their main page forever (although that seems unlikely, actually).
    That is impressive. Much higher resolution than I was expecting.

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    I had thought that they were going to do Sgr A* as their first target. M87's is 1/3 the angular diameter of our central black hole. I am guessing this means that Sgr A* is too inactive to produce an interesting telltale image.
    Hurray for the EHT team for their huge effort to get this image!
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    Quote Originally Posted by philippeb8 View Post
    Oh that’s fine. We lost a battle but not the war


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    well I haven't even lost a battle there, as with my thinking on the subject, the object would look no different, than an event horizon model prediction.
    ................................

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    Quote Originally Posted by antoniseb View Post
    I had thought that they were going to do Sgr A* as their first target. M87's is 1/3 the angular diameter of our central black hole. I am guessing this means that Sgr A* is too inactive to produce an interesting telltale image.
    I was surprised as well.

    Quote Originally Posted by antoniseb View Post
    Hurray for the EHT team for their huge effort to get this image!
    Agreed!
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    Lightbulb The Event Horizon Telescope Resolves the Black Hole in M87

    No thread on this yet?

    Anyway, after the Higgs Boson and Gravitational Waves, the next revolutionary result from high energy (astro)physics:

    The Event Horizon Telescope, a Very Long Baseline Interferometry network working at 1.3 mm (90 GHz), has resolved the supermassive black hole at the core of M87 (in the Virgo Cluster)! It is the first direct image of a black hole, and so far it matches the predictions of Einsteinian General Relativity perfectly.

    Press Conference:
    https://www.youtube.com/watch?v=Dr20f19czeE

    ESO Press Release:
    https://www.eso.org/public/news/eso1907/

    Astrophysical Journal Letters issue with the first six core papers - Open Access!
    https://iopscience.iop.org/issue/2041-8205/875/1

    A few quick observations:
    - Interesting that they published this in ApJ Letters, and seemingly not in Nature or Science (well, at least one paper featuring the central result).
    - Similar to some of the ApJ Letters papers on GW170817, these things hardly fit the definition of Letters, they're massive! The first paper is 17 pages (the last 8 are acknowledgements, author list and affiliations, references, ORCIDs...), the rest are 30 to 50 each!
    - Let's see what the Woo Woos have to say about this one.

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    The first picture of a black hole opens a new era of astrophysics

    This is what a black hole looks like.

    A world-spanning network of telescopes called the Event Horizon Telescope zoomed in on the supermassive monster in the galaxy M87 to create this first-ever picture of a black hole.

    “We have seen what we thought was unseeable. We have seen and taken a picture of a black hole,” Sheperd Doeleman, EHT Director and astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., said April 10 in Washington, D.C., at one of seven concurrent news conferences. The results were also published in six papers in the Astrophysical Journal Letters.

    “We’ve been studying black holes so long, sometimes it’s easy to forget that none of us have actually seen one,” France Córdova, director of the National Science Foundation, said in the Washington, D.C., news conference. Seeing one “is a Herculean task,” she said.
    Also moving this from Q&A to Astronomy since it's like to engender discussion beyond the initial question.
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    Very impressive. I'm not sure what they expected the image to look like.

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    Quote Originally Posted by Strange View Post
    That is impressive. Much higher resolution than I was expecting.
    Actually, that is smoothed with a 20 mu arcsec Gaussian kernel. The true resolution is just some pixels.

    Quote Originally Posted by antoniseb View Post
    I had thought that they were going to do Sgr A* as their first target. M87's is 1/3 the angular diameter of our central black hole. I am guessing this means that Sgr A* is too inactive to produce an interesting telltale image.
    Hurray for the EHT team for their huge effort to get this image!
    Hm, I had always heard the two angular diameters were about the same? They stated "The MW black hole is 1000 times smaller but 1000 times closer." The main issue seems to be that the variability of Sgr A* is way too high. With a light-crossing time of about 7 minutes (I was told), the thing flickers way too much considering the long, deep exposures that are needed. The variability timescale of M87* is weeks, so it "sits still" while you "take the picture."

    Quote Originally Posted by ToSeek View Post
    The first picture of a black hole opens a new era of astrophysics

    Also moving this from Q&A to Astronomy since it's like to engender discussion beyond the initial question.
    Ah, this explains why I did not find a thread in the Astronomy forum! Is it possible to merge my post into this thread?

    Quote Originally Posted by bknight View Post
    Very impressive. I'm not sure what they expected the image to look like.
    Just like this one. There's a figure in the main paper showing simulation results from numerical models which are then convolved with the observational and telescope factors, the end results look essentially exactly like the real image.
    Last edited by Don Alexander; 2019-Apr-10 at 07:14 PM.

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    Quote Originally Posted by antoniseb View Post
    I had thought that they were going to do Sgr A* as their first target. M87's is 1/3 the angular diameter of our central black hole. I am guessing this means that Sgr A* is too inactive to produce an interesting telltale image.
    Hurray for the EHT team for their huge effort to get this image!
    Seems that "they" are working on that image.

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    Quote Originally Posted by Don Alexander View Post
    Ah, this explains why I did not find a thread in the Astronomy forum! Is it possible to merge my post into this thread?
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    1. If you are going to do anything original with a black hole, do it with the great-granddaddy of them all, M87.

    2. Correct me if I am wrong, this is not the black hole itself, it is the shadow of the black hole cast against surrounding dust and gas, created by starlight coming from the other side of the black hole? Or what? It's the effects caused by the black hole and surrounding medium, not the hole itself.
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    Both xkcd and Google are getting in on the act.

    xkcd: https://xkcd.com/2135/
    google: https://www.google.com/logos/doodles...0528.2-2xa.gif
    Last edited by schlaugh; 2019-Apr-10 at 09:51 PM. Reason: link update

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    Quote Originally Posted by Roger E. Moore View Post
    2. Correct me if I am wrong, this is not the black hole itself, it is the shadow of the black hole cast against surrounding dust and gas, created by starlight coming from the other side of the black hole? Or what? It's the effects caused by the black hole and surrounding medium, not the hole itself.
    It is the black hole and the bright ring is the accretion disk. We are looking at it from almost the axial direction, which is why the ring is nearly symmetrical.

    But it is slightly more complex than that. The black area is larger than the event horizon - it is the area where light cannot escape, ie. the photon sphere - so 1.5 times larger than the event horizon. That is why (rather inaccurately) it is called a shadow.

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    Quote Originally Posted by Strange View Post
    That is why (rather inaccurately) it is called a shadow.
    Ooooooh, makes sense now. Thank you.
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
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    Quote Originally Posted by Strange View Post
    It is the black hole and the bright ring is the accretion disk. We are looking at it from almost the axial direction, which is why the ring is nearly symmetrical.

    But it is slightly more complex than that. The black area is larger than the event horizon - it is the area where light cannot escape, ie. the photon sphere - so 1.5 times larger than the event horizon. That is why (rather inaccurately) it is called a shadow.
    Veritasium did a really good video explaining the architecture of these terrifying abysses.

    This is a New Horizons moment. Science books were changed forever whenever we finally had good images of Pluto to put in them. Now, the same goes for black holes.

    Next step is to put a telescope on the Moon for even better interferometry. Imagine what could be done with an aperture a light second across.

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    Quote Originally Posted by Glom View Post
    Next step is to put a telescope on the Moon for even better interferometry. Imagine what could be done with an aperture a light second across.
    Rather a large step, unfortunately.

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