This is actually what the accretion disk looks like when gravity indeed does warp the light. The bright, persistent ring is a consequence of strong gravitational lensing of the accretion disk, appearing as a thin ring feature superimposed atop the broader accretion disk seen in the image.
Hello, I watched your talk at the Royal Institute about black holes and the Event Horizon Telescope. It was amazing! I have a question that was not part of the Q&A afterwards. I hope you can answer: You talked about the dynamics of the black hole at the center of Milky Way, and that it was on the order of minutes (I assume the dynamics of the accretion disc). The dynamics of the M87 black hole was said to be in the order of days, and you explained why that makes it much harder to synthesize images of the Sag A* black hole than M87. I understand that part, but here is my question: Would it be possible to use the Earth - Sun baseline as the Earth revolves around the Sun and the same type of interferometry and image synthesis looking at the M87 black hole that was used for Sag A*? If the "dynamics" of Sag A* is minutes and it is days for M87, that would be like comparing days to months for using the Earth-Sun baseline for imaging M87 (60 minutes per hour * 24 hours a day = 1440 minutes in a day, and 6 months is about 180 days so the Earth-Sun baseline is almost a factor of 10 better for M87 than what you were doing for Sag A*). I understand there are a lot of things I don't understand, of course, but I hope you can answer. Thanks.
Note: When I say "better" above, I mean the difficulty of the dynamical situation, not the advantage of using the Earth - Sun baseline at 150 million km * 2 vs the diameter of the Earth at 12 000 km.
Thank you, I'm glad you enjoyed the talk! (Royal Institution talk here: ruclips.net/video/fGGW-kwc2n0/видео.html) The major difficulty in using very long baseline interferometry (VLBI) for Sgr A* is that the source is changing so rapidly, potentially on timescales of a few minutes close to the event horizon. The VLBI technique requires that the source is effectively static (unchanging) over the duration of the observations. This was true for M87, but is of course not the case for Sgr A*. Extending the array to have very long (Earth-Sun) baselines as you propose would certainly improve the sensitivity to emission structures close to the event horizon, which if achievable would be transformative for studies of M87. However this approach cannot overcome the inherent issues with the structural variability of Sgr A*. VLBI (i.e., Earth rotation aperture synthesis) is not formulated for such a dynamical source, so the Event Horizon Telescope team had to compensate for Sgr A*'s "intraday variability" through the injection of a variability noise model. Please see, e.g., Section 3.2 of iopscience.iop.org/article/10.3847/2041-8213/ac6429 for more information on this. I hope this helps!
By "hoop" I believe you're referring to the bright orange "doughnut" seen in the EHT images. The reason this movie doesn't look like that is because it simulates what we would see with a perfect, infinite resolution radio telescope. The EHT image of Sgr A* is "blurry" because of the finite angular resolution of the telescope array. There is a limit to the scales we can presently resolve: around 20 micro-arcseconds, which is roughly 2 Schwarzschild radii (around half the diameter of the bright ring in this movie). Anything smaller than this scale cannot be resolved yet, hence the blurry image. But this movie shows you what we expect to see if we weren't limited by this resolution, i.e., if we had infinite/perfect resolution. As resolution improves the hoop/doughnut is expected to become thinner and sharper, more reminiscent of a thin, bright ring, with turbulent and variable matter swirling around it, as seen in this movie.
![Falling into a black hole (Realistic Ultra HD 360 VR movie) [4K]](http://i.ytimg.com/vi/S6qw5_YA8iE/mqdefault.jpg)
so beautiful. great explanation of what we are seeing. thank you!
Terrific. Thank you!
I love space so much
i want to live in there
Congrats! How long does something like this take to compute and render?
Thank you! In total, several weeks, running on supercomputers around the world.
Great stuff! Thank you!
Is this what accretion disk looks like without gravity warping the light?
This is actually what the accretion disk looks like when gravity indeed does warp the light. The bright, persistent ring is a consequence of strong gravitational lensing of the accretion disk, appearing as a thin ring feature superimposed atop the broader accretion disk seen in the image.
Hello, I watched your talk at the Royal Institute about black holes and the Event Horizon Telescope. It was amazing!
I have a question that was not part of the Q&A afterwards. I hope you can answer:
You talked about the dynamics of the black hole at the center of Milky Way, and that it was on the order of minutes (I assume the dynamics of the accretion disc). The dynamics of the M87 black hole was said to be in the order of days, and you explained why that makes it much harder to synthesize images of the Sag A* black hole than M87. I understand that part, but here is my question: Would it be possible to use the Earth - Sun baseline as the Earth revolves around the Sun and the same type of interferometry and image synthesis looking at the M87 black hole that was used for Sag A*?
If the "dynamics" of Sag A* is minutes and it is days for M87, that would be like comparing days to months for using the Earth-Sun baseline for imaging M87 (60 minutes per hour * 24 hours a day = 1440 minutes in a day, and 6 months is about 180 days so the Earth-Sun baseline is almost a factor of 10 better for M87 than what you were doing for Sag A*).
I understand there are a lot of things I don't understand, of course, but I hope you can answer. Thanks.
Note: When I say "better" above, I mean the difficulty of the dynamical situation, not the advantage of using the Earth - Sun baseline at 150 million km * 2 vs the diameter of the Earth at 12 000 km.
Thank you, I'm glad you enjoyed the talk! (Royal Institution talk here: ruclips.net/video/fGGW-kwc2n0/видео.html)
The major difficulty in using very long baseline interferometry (VLBI) for Sgr A* is that the source is changing so rapidly, potentially on timescales of a few minutes close to the event horizon. The VLBI technique requires that the source is effectively static (unchanging) over the duration of the observations. This was true for M87, but is of course not the case for Sgr A*.
Extending the array to have very long (Earth-Sun) baselines as you propose would certainly improve the sensitivity to emission structures close to the event horizon, which if achievable would be transformative for studies of M87. However this approach cannot overcome the inherent issues with the structural variability of Sgr A*. VLBI (i.e., Earth rotation aperture synthesis) is not formulated for such a dynamical source, so the Event Horizon Telescope team had to compensate for Sgr A*'s "intraday variability" through the injection of a variability noise model. Please see, e.g., Section 3.2 of iopscience.iop.org/article/10.3847/2041-8213/ac6429 for more information on this.
I hope this helps!
@@ZiriYounsi Many thanks! I will read the document you referred to.
Thank you so much
Coooooolll
why there is no hoop in there?
By "hoop" I believe you're referring to the bright orange "doughnut" seen in the EHT images. The reason this movie doesn't look like that is because it simulates what we would see with a perfect, infinite resolution radio telescope. The EHT image of Sgr A* is "blurry" because of the finite angular resolution of the telescope array. There is a limit to the scales we can presently resolve: around 20 micro-arcseconds, which is roughly 2 Schwarzschild radii (around half the diameter of the bright ring in this movie).
Anything smaller than this scale cannot be resolved yet, hence the blurry image. But this movie shows you what we expect to see if we weren't limited by this resolution, i.e., if we had infinite/perfect resolution. As resolution improves the hoop/doughnut is expected to become thinner and sharper, more reminiscent of a thin, bright ring, with turbulent and variable matter swirling around it, as seen in this movie.