First image of a black hole: a CNRS researcher had simulated it as early as 1979(cnrs.fr)
cnrs.fr
First image of a black hole: a CNRS researcher had simulated it as early as 1979
https://www.cnrs.fr/en/first-ever-image-black-hole-cnrs-researcher-had-simulated-it-early-1979
40 comments
Ugh it must have been so satisfying to take all that science and data and generate an image like that in 1979.
I wish they covered more technical detail into how and with what tools the image was generated. Anyone know?
See the paper mentioned by @grafelic
BitwiseFool(8)
I used the IBM 7040 mainframe
of Paris-Meudon Observatory, an early transistor computer with punch card inputs. The
machine generated isolines that were directly translatable as smooth curves using the
drawing software available at the time.
From Luminets personal recollections on black hole imaging: https://arxiv.org/pdf/1902.11196.pdf
From Luminets personal recollections on black hole imaging: https://arxiv.org/pdf/1902.11196.pdf
Great read, thank you. It goes on ...
"The first step was to integrate the equations of light ray trajectories in Schwarzschild space-time and draw the isoradial curves (i.e. at constant radial distance from the black hole) of a thin disk around the black hole, as they would be seen by an observer above the disk's plane" ....
"The final black and white "photographic" image was obtained from this pattern. Lacking of an appropriate drawing software, I had to create it by hand. Using numerical data from the computer, I drew directly on negative paper with pen and Indian ink,placing dots more densely where the simulation showed more light (a few thousands dots for the full plate). Next, I took the negative of my negative to get the positive, the black points becoming white and the white background becoming black. The result converged into the pleasantly organic, asymmetrical form reproduced in Figure 8, both visually engaging and scientifically revealing."
I am feeling grateful to have started by scientific/engineering computing career one year later than the authors paper in 1980, and as it happens the first year without punched cards at my Univ.
"The first step was to integrate the equations of light ray trajectories in Schwarzschild space-time and draw the isoradial curves (i.e. at constant radial distance from the black hole) of a thin disk around the black hole, as they would be seen by an observer above the disk's plane" ....
"The final black and white "photographic" image was obtained from this pattern. Lacking of an appropriate drawing software, I had to create it by hand. Using numerical data from the computer, I drew directly on negative paper with pen and Indian ink,placing dots more densely where the simulation showed more light (a few thousands dots for the full plate). Next, I took the negative of my negative to get the positive, the black points becoming white and the white background becoming black. The result converged into the pleasantly organic, asymmetrical form reproduced in Figure 8, both visually engaging and scientifically revealing."
I am feeling grateful to have started by scientific/engineering computing career one year later than the authors paper in 1980, and as it happens the first year without punched cards at my Univ.
Amazing. Kip Thorne's simulation for the movie Interstellar took "a year of work by 30 people and thousands of computers." Of course, that was also an animated simulation with a high level of visual detail.
https://www.wired.com/2014/10/astrophysics-interstellar-blac...
https://www.wired.com/2014/10/astrophysics-interstellar-blac...
In the comparison image M87's blackhole has an almost perfectly circular black spot, while in the simulated image the center is half a circle due to the disk. Is this caused by some missing effect in the calculations, the angle of the disk, or something else?
We're looking down on M87* from one of its poles. The image from the paper is viewed close to the equator.
I never understood this, do black holes have poles from any distance?
I know if you're too close, everything gets distorted, but I would have thought they look the same from any direction or angle, never managed to grasp the concept.
Maybe there is some 3d sim to explain this?
I know if you're too close, everything gets distorted, but I would have thought they look the same from any direction or angle, never managed to grasp the concept.
Maybe there is some 3d sim to explain this?
The stuff falling onto the black hole has an orientation -- it forms an accretion disk at the "equator".
If the black hole is spinning, it has poles. We expect all black holes to be spinning. This is a subtle change in the shadow itself, but...
And if the accretion disk and black hole have misaligned poles, there should be a huge warp in the disk close to the black hole as the black hole frame-drags the accretion disk.
If the black hole is spinning, it has poles. We expect all black holes to be spinning. This is a subtle change in the shadow itself, but...
And if the accretion disk and black hole have misaligned poles, there should be a huge warp in the disk close to the black hole as the black hole frame-drags the accretion disk.
Is the misalignment _necessary_? I always thought the hole got its rotation from the infalling matter.
Over billions of years, the angular momentum of the stuff falling in changes.
But if it's infinitely small(not the event horizon, the black holes singularity), then a rotation or poles are hard to imagine. Is the singularity rotating or the whole event horizon area?
It's hard to put this in descriptive words, i hope my point gets across.
Yeah I thought about this and looked into it a little bit. A "point" has zero dimensions so my intuition thought that there's nothing TO spin.
What happens at the singularity in a rotating black hole depends on your quantum theory of gravity. Some theories have the singularity as a "ring" instead of a point. I believe loop quantum gravity has a "planck star" in the center of a black hole.
Macroscopically, rotating black holes can be thought of as rotating the space around the event horizon. So the spacetime curvature doesn't just pull you directly to the center, there's an angular aspect as well.
https://en.wikipedia.org/wiki/Planck_star
https://www.youtube.com/watch?v=UjgGdGzDFiM
What happens at the singularity in a rotating black hole depends on your quantum theory of gravity. Some theories have the singularity as a "ring" instead of a point. I believe loop quantum gravity has a "planck star" in the center of a black hole.
Macroscopically, rotating black holes can be thought of as rotating the space around the event horizon. So the spacetime curvature doesn't just pull you directly to the center, there's an angular aspect as well.
https://en.wikipedia.org/wiki/Planck_star
https://www.youtube.com/watch?v=UjgGdGzDFiM
I’m only an enthusiast, but my understanding is that it’s the black hole’s rotation that causes poles in 3D. The visible accretion disc, I believe lies in the plane in which the black hole rotates.
If the black hole is not spinning, it should look the same from every angle. A spinning black hole is deformed (like the spinning Earth.)
Anyway, we are not seeing the black hole (because it looks just like a black circle in front of a black background). The interesting part of the image is a disk of material spinning around it. There is a nice 3d cardboard simulation and clear explanation in a video by Veritasium https://www.youtube.com/watch?v=zUyH3XhpLTo
Anyway, we are not seeing the black hole (because it looks just like a black circle in front of a black background). The interesting part of the image is a disk of material spinning around it. There is a nice 3d cardboard simulation and clear explanation in a video by Veritasium https://www.youtube.com/watch?v=zUyH3XhpLTo
Is the code freely available someplace? I found papers that talk about the math but I don't understand the math...
This needs to be reimplemented in JavaScript
This would be an amazing album cover.
Very Long Baseline radio astronomy has been around for decades. One of its early accomplishments was the realtime observation of plate tectonics motion between telescopes. These days that is observed routinely with high resolution GPS.
One EHT speaker I asked said an important advance was scaling up the VBLI procedure a thousand times from hundreds of megahertz to hundreds of gigahertz to achieve resolutions needed to image the three largest super massive black holes. This involves huge improvements across the entire system from the antenna receiver, clock resolution and petabyte data handling.
One EHT speaker I asked said an important advance was scaling up the VBLI procedure a thousand times from hundreds of megahertz to hundreds of gigahertz to achieve resolutions needed to image the three largest super massive black holes. This involves huge improvements across the entire system from the antenna receiver, clock resolution and petabyte data handling.
The EHT can resolve the two super massive black holes which are the largest on the sky. The Milky Way's SMBH is a relatively small one, but it's close enough to make up for that.