How to Understand the Image of a Black Hole 3 months ago   09:19

We have just seen the first image of a black hole, the supermassive black hole in the galaxy M87 with a mass 6.5 billion times that of our sun. But what is that image really showing us?

This is an awesome paper on the topic by J.P. Luminet:
Image of a spherical black hole with thin accretion disk
Astronomy and Astrophysics, vol. 75, no. 1-2, May 1979, p. 228-235

Using my every day intuition I wondered: will we see the "shadow" of the black hole even if we're looking edge on at the accretion disk? The answer is yes because the black hole warps space-time, so even if we wouldn't normally be able to see the back of the accretion disk, we can in this case because its light is bent up and over the black hole. Similarly we can see light from the bottom of the back of the accretion disk because it's bent under the bottom of the black hole. Plus there are additional images from light that does a half turn around the black hole leading to the inner rings.

What about the black hole "shadow" itself? Well initially I thought it can't be an image of the event horizon because it's so much bigger (2.6 times bigger). But if you trace back the rays, you find that for every point in the shadow, there is a corresponding ray that traces back to the event horizon. So in fact from our one observing location, we see all sides of the event horizon simultaneously! In fact infinitely many of these images, accounting for the virtually infinite number of times a photon can orbit the black hole before falling in. The edge of the shadow is due to the photon sphere - the radius at which light goes around in closed orbits. If a light ray coming in at an oblique angle just skims the photon sphere and then travels on to our telescopes, that is the closest 'impact parameter' possible, and it occurs at sqrt(27)/2*r_s

Huge thanks to:
Prof. Geraint Lewis
University of Sydney
Like him, I'm hoping (predicting?) we'll see some moving images of black holes tomorrow

Prof. Rana Adhikari

Riccardo Antonelli - for excellent images of black holes, simulations and ray-tracing code, check out:

The Event Horizon Telescope Collaboration
Check out their resources and get your local link for the livestream here:

Special thanks to Patreon supporters:
Donal Botkin, Michael Krugman, Ron Neal, Stan Presolski, Terrance Shepherd, Penward Rhyme

Filming by Raquel Nuno
Animation by Maria Raykova

Comments 7492 Comments

OK, just over an hour to go! This is the link to the Washington DC National Science Foundation livestream:
Click here for links to other live streams (there are several available in different countries):
I guess thanks to YT for their recommendations. Great videos.
Jae Watkins
Can someone check my math?
Assuming M87 has a mass of 4.47 x 10^42kg (got this number from converting solar mass number to kg)
Would the rS = 7.07 x 10^12km? Roughly? I can’t seem to find the answer anywhere
Austin Fox
How do physical rings form around any celestial body limited to a specific plane? If there’s no up or down and all position is relative why does the ring form how it does? It makes more sense in my caveman brain for spherical rings expanding in all help explain this to me PLEASE
Crispin Koech
+1 for the interstellar example.
Robert Devino
That's easy first look at it and you should recognize the natural shape of a plasmoid! Well that is unless of course you are a pseudo scientist that believes in fairy-tale things like black holes and Dark Matter. Plasma Science and the Electric Universe theory explain this and many other things we see in the universe without invoking magic ! When gravity based cosmologists are befuddles by what they find. Electric Universe Scientists are smiling because what is found is what they predicted !!!!! They don't have to constantly create had hock fixes to theories because of how many things they find that exist that contradict their theories! The idea that the ruling force in the universe is out dates and has so many holes in it that they should have admitted a long time ago it is wrong! But they can't do that because their diplomas value and the funding is all tied to those disproved theories! They can't admit they are wrong ! If they do they are ruined! But we seriously need to stop funding all this antiquated Einstein inspired research and focus more on what Tesla tried to show us! WE are wasting billions of dollars and untold time with this misguided science! You show me how to get an infinitely dense singularity without illegal math operations and randomly inserting planks constant and maybe I will listen then. I mean you are not even following the simplest and most basic of math rules and you want people to buy it because you say so????? You guys can't even get a computer model to produce a super nova. There is never enough rebound pressure to create the explosion. You have to manipulate the programming to get it to go??? Take a hint!!!
Salahudin Tsabit
i wish stephen hawking can see that
Can anyone explain this?
workout hard
Sir you are awesome
Sabine Bilka
This answers the question I have had since the black hole image has been released, and the explanation is cristal clear, thank you so much
Saji baskar
Black holes can't just like center of whirlpool??
one of my friend who is in Commerce stream .. shared the image and captioned it "happiest moment!! woow!! this is an enormous achievement"
and then I commented below "dude.. cm'on!! what type of happiness do YOU get from this....i mean u ppl deal with balance sheet and business... right?"
He didn't talk to me since then!!
One thing I don't understand about black holes. How can anything ever go inside the event horizon? Since time slows down more and more the closer you come to the event horizon, an outside observer should _never_ see anything go past the horizon. But everywhere you hear people talk about stuff being sucked into black holes. In this video he talks about something "very quickly going into the black hole". How can this be true? I'm sure I am misunderstanding something about black holes.
Captain America
It’s Thanos.
Furnace Furn
This guy can science!
He's smart!
My new favourite!
JAG 0937 EB
nonsense, black holes are flat
Abel SM
They were planning to take Marzia's camera but they accidentally took Felix's
Vítor Salles
it just amazes me how perfect was your explanation compared to the actual picture. Thank you so much!
Extremely hard to wrap your head around. Fascinating indeed.
Awesome video bro! Love it!
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How to Understand the Image of a Black Hole 3 months ago   11:37