Of Particular Significance

A Black Day (and a Happy One) In Scientific History

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 04/10/2019


Twenty years ago, astronomers Heino Falcke, Fulvio Melia and Eric Agol (a former colleague of mine at the University of Washington) pointed out that the black hole at the center of our galaxy, the Milky Way, was probably big enough to be observed — not with a usual camera using visible light, but using radio waves and clever techniques known as “interferometry”.  Soon it was pointed out that the black hole in M87, further but larger, could also be observed.  [How? I explained this yesterday in this post.]   

And today, an image of the latter, looking quite similar to what we expected, was presented to humanity.  Just as with the discovery of the Higgs boson, and with LIGO’s first discovery of gravitational waves, nature, captured by the hard work of an international group of many scientists, gives us something definitive, uncontroversial, and spectacularly in line with expectations.

An image of the dead center of the huge galaxy M87, showing a glowing ring of radio waves from a disk of rapidly rotating gas, and the dark quasi-silhouette of a solar-system-sized black hole.  Congratulations to the Event Horizon Telescope team

I’ll have more to say about this later [have to do non-physics work today 🙁 ] and in particular about the frustration of not finding any helpful big surprises during this great decade of fundamental science — but for now, let’s just enjoy this incredible image for what it is, and congratulate those who proposed this effort and those who carried it out.


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21 Responses

  1. A great article, thanks !

    Somewhat off topic (sorry !) ;
    any idea if a very small black hole (via Hawking radiation ?)
    in collision with, say, a much larger star, would eventually
    consume the star ?

    1. The black hole will pass right through the star unless the relative velocities are very slow and the black hole manages to eat a substantial amount of material going through. Only in those very rare circumstances will it stay within the star. In that case it will eventually eat the star, but the rate at which it does so can be very slow, and depends very greatly on how small or large it is. So there is no simple answer. There is some relevant discussion and references in Giddings and Mangano from maybe 2008.

  2. There are so much confirmation of general relativity in the press conference and papers, and even when they cannot really reject other theories it comes up simplest such as when they think the shadowing object is really a black hole. I did not know general relativity scaled nicely, which may explain why the theorist in the video pressed on the 7 orders of magnitude between LIGO black holes and this one.

    The press conference argument between scientists on the jet mechanism (magnetic field compression or frame dragging) was interesting, and I note the paper push the ergosphere frame dragging as the consensus. Lots of pearls for outsiders!

  3. The photo bothers me. A news report says the photo is 25 billion miles across.

    To me that suggests that the glowing gas is exactly like the gas of a nebula ionised by radiation (of infalling material).

    However this is not some tiny accretion disk but is of massive proportions. I would guess this is gas and dust is in a stable orbit around the black hole, as planets are in stable orbits around stars. Yes, things can orbit a black hole for probably millions of years and more.

    And that the actual black hole is a very tiny dot inside the small black circle we see.

    Short of a black hole swallowing a star, many are quiet most of the time with a little interstellar material falling in. Which also suggests this is quiet and that the actual BH is tiny. Where are the plasma jets of material in an active BH from both poles?

    1. The black hole in question is over a billion miles across and has been further magnified by lensing. Your intuition is wrong

      The plasma jets may not be visible for several possible reasons. I don’t know which is the cause and I’m not sure the scientists do either, yet. But I will try to find out.

    1. A black hole is just a very massive star that has run out of fuel and so collapsed in on itself. The nearest one to us is just 3,000 light years away.

      The lack of symmetry suggests just how big that gaseous nebula around the black hole is, that the gravity of the BH has not got control of it.

  4. Is the lack of symmetry local, at the black hole, or because gravitational lensing in transit to earth?

    Again, I have to ask, is gravity a real force or the effect of the other forces influence on space, bending space? I would not invalid Einstein because his equations merely formulated this influence.

    1. I am not sure what lack of symmetry you refer to. The press conference pressed on how symmetric – circular – the shadow is, which is one of the very many ways general relativity was confirmed (or else, including producing the black hole) was the simplest alternative).

      They also discussed the large asymmetry in emission, which was caused by the black hole rotation – mainly through ergosphere frame dragging, I think – projected onto our field of view. (The black hole is now believed to be rotating clockwise with the rotation axis pointing away from us; dunno how much angled that projection is.)

      And the papers discuss that some remaining asymmetries may be caused by physics that we can learn more of.

      Finally, the emission is from an accretion disk that is likely asymmetrically fed by differing amounts of gas (and shredded stars) falling in from different directions.

  5. Hi, Fantastic presentation. But there are an missing images of Neutron star, a pre-Black Hole, to complete such studies. The most interesting images, not presented, would be of the horizon event, near the singularity, that orbit the BN, to explained and teaching such formation, growth and gravitational action of BH. These would be the best for studies. an example to be investigated: knowing that the BN brings its prey (matter) in the form of swirling, spinning motion, and why it is always in a single direction? What does this direction do? Better, if it is on 360º, why does it form a single horizon? That is, in matter outside this horizon or line, I say at 90º, or below, why it should aligns with that horizon? Why, if BH is an “ball”? That is like everything on earth was swallowed up only in Ecuador, and never by the poles, so why? I hope you undestand it. Thanks

    1. Adding: if BH were evolved in a mass at globe form, we would never see the background, the BH, that is, the image proves to be a plane horizon, never a cloud globe of matter being swallowed.

        1. Nobel and Fields Medal to Katie Bouman that develop the algorithms that made the full black hole image possible. A genius

          1. I do not think there will be a Nobel prize for this photo, but if there were to be one, it would go to people who many years ago pointed out that this method would be possible. Dr. Bouman’s work is commendable, but in the media’s rush to create heroes and heroines, she is being given too much credit right now (as she herself has stated) for the collective work of 200 people. You can only make an image based on data — and someone has to collect that data, which is only possible with an extraordinary level of effort and cleverness by people whose names have not even been mentioned.

          2. Perfect Dr Matt. But lets watch hers beatiful explanation about it on youtube “How to take a picture of a black hole Katie Bouman” (this subject will still give much comment on the world, for many time, incredible disclosure)

  6. It’s a fantastic day for fundamental astrophysics experimental (very long baseline interferometry + computer data processing) & phenomenological (GR + magnetohydrodynamic simulations) indeed. But the beautiful M87 black hole’s silhouette hides also the lack of a SgrA* picture …. that may have been delayed by some down to earth human issues like https://phys.org/news/2019-02-astronomers-victims-mexico-violence-crime.html
    Looking forward to reading your take on the last great decade of fundamental science, may be not as frustrating as it seems.

    1. Indeed, that is a big question mark. The loss of that telescope could be a problem going forward, but they made measurements back in 2017 I believe. The sense I had from what they said today is that they may be having trouble with the fact that the source varies over time scales comparable to the time to make the measurement… but they were cagey enough not to be entirely clear about it.

      1. Yes indeed as reported in https://iopscience.iop.org/article/10.3847/2041-8213/ab0ec7: “Sgr A*, has a precisely measured mass three orders of magnitude smaller than that of M87*, with dynamical timescales of minutes instead of days. Observing the shadow of Sgr A* will require accounting for this variability and mitigation of scattering effects caused by the interstellar medium (Johnson 2016; Lu et al. 2016; Bouman et al. 2018).”

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