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Unveiling the first-ever image of a black hole [video]

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Re: Unveiling the first-ever image of a black hole [video]

#371

Post by ants_a »

julienchastang wrote: post #359
nonbel wrote: post #251

It doesn't sound like they just snapped a picture. The one guy says they used "supercomputers" for 6 months to get the image. Sunspots look black relative to the rest of the sun but are actually very bright. Could this be the same thing? How did they set the black level? Is there a description of the procedure somewhere? EDIT: Found the paper describing the data processing: https://iopscience.iop.org/article/10.3847/…

Indeed, from what I gather from this thread and external links this “image” seems to be more of a plot than an image. In fact, are we looking at a matplotlib plot of the data with a “hot” colormap? The iopscience paper even references matplotlib. I’m just making some educated guesses here, but it’s still fun to think about. BTW: Python for the win! iopscience paper makes several references to Python tools (e.g., nump…

Every image is a plot... This one just has had a bit more processing gone into it than your average demosaiced and noise reduced vacation photo.

Re: Unveiling the first-ever image of a black hole [video]

#372

Post by bbrks »

dugluak wrote: post #325

Why did they choose this very distant galaxy? why not something that's close to us like the andromeda galaxy or even the center of our own galaxy?

They did. M87* was the widely publicised "first" photo, but they also got images of Sagittarius A* (the supermassive black hole at the center of our galaxy).

The difficulties with Sgr A* are twofold:

- The black hole moves too much during an observation (because it's much closer, and parallax is a thing)

- Sgr A* is much smaller than M87* by mass, so even though it's much closer, the angular diameter is almost the same, and the accretion disk is dimmer.

Re: Unveiling the first-ever image of a black hole [video]

#373

Post by kerbalspacepro »

vertline3 wrote: post #368

So how come it's a ring of plasma that forms and not a sphere? Like we can see the hole unobstructed? Is it because gravity tends to clump things together? I guess Saturn's rings are the same?

Conservation of Angular momentum collapses shapely sort of things into a disk

Re: Unveiling the first-ever image of a black hole [video]

#375

Post by koheripbal »

GuB-42 wrote: post #223
JumpCrisscross wrote: post #27

Good video that correctly predicted the image and describes why it looks the way it does [1]. TL; DR The dark area is the entire surface of the event horizon, including the side facing away from us, plus some more due to photons missing the event horizon "directly" being drawn in. One side is brighter due to its being Doppler boosted. [1] https://www.youtube.com/watch?v=zUyH3XhpLTo

Smart move by Veritasium, making a video commenting the news just before the news actually happens. Time works in weird ways around black holes. Anyways, it is a good one. So is that channel in general. It is also a good video if you just watched Interstellar, because it also explains why the black hole looks the way it does in the movie. Note that the movie black hole rendering is slightly incorrect for artistic rea…

It's too bad we cannot see the accretion disk edge-on as in the video. That would have made it a perfect prediction. Maybe it's so thin that it's overwhelmed by the projections of the top and bottom of the back side of the disk.

Re: Unveiling the first-ever image of a black hole [video]

#377

Post by petschge »

vertline3 wrote: post #368

So how come it's a ring of plasma that forms and not a sphere? Like we can see the hole unobstructed? Is it because gravity tends to clump things together? I guess Saturn's rings are the same?

Saturns ring, the flattening of the accretion disk, the fact that planet systems will have most planets more or less in one plane and that spiral galaxies are flat (much thinner than they are wide at least) all have the same reason, yes. Basically most orbits align due to initial orbital momentum and the stuff that orbits in other directions sooner or later experiences enough friction to be forced into the common orbital plane.

Re: Unveiling the first-ever image of a black hole [video]

#378

Post by alpaca128 »

pjungwir wrote: post #365
trickstra wrote: post #224

Earlier quoted context omitted.

perpendicular - we see it almost exactly from the top. Mentioned during the Q&A (41:33 to be exact)

The video JumpCrisscross shared above says this is the black hole at the center of our galaxy, so why isn't its accretion disk oriented the same as the rest of the galaxy? Isn't that weird?

It's actually in a galaxy called Messier 87 which is 55 million lightyears away.

Re: Unveiling the first-ever image of a black hole [video]

#380

Post by pjungwir »

alpaca128 wrote: post #378
pjungwir wrote: post #365

Earlier quoted context omitted.

The video JumpCrisscross shared above says this is the black hole at the center of our galaxy, so why isn't its accretion disk oriented the same as the rest of the galaxy? Isn't that weird?

It's actually in a galaxy called Messier 87 which is 55 million lightyears away.

Oh, interesting! Wouldn't it be easier to photograph our own? :-)
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