We have images of two black holes so far, with representations showing a deep black center where in-falling matter vanishes- how would that look side on? Would it be possible to even obtain an image of it?
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$\begingroup$ upload.wikimedia.org/wikipedia/commons/6/60/… $\endgroup$– safesphereCommented May 15, 2022 at 6:29
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$\begingroup$ @safesphere that may indeed be what the OP has in mind, but it is an image of a physically thin, optically thick disk. The disks (in the case of M87 and Sgr A*) are optically thin and physically thick. $\endgroup$– ProfRobCommented May 15, 2022 at 9:13
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$\begingroup$ @ProfRob Sure a real picture would be blurrier than ideal, but how do we know what the disks are around these black holes? Making any conclusions based on the 3x3-pixel images of the EH project is premature to say the least. $\endgroup$– safesphereCommented May 15, 2022 at 17:02
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$\begingroup$ @safesphere I am not referring to the resolution of the image. The link you have given is the representation of a disk that is not like the ones around M87 and Sgr A*. i.e. Different geometry and different physical conditions. $\endgroup$– ProfRobCommented May 15, 2022 at 18:12
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$\begingroup$ @ProfRob How do we know what type of disks are around these black holes? Based on what? $\endgroup$– safesphereCommented May 16, 2022 at 3:26
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1 Answer
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You would still see a ring, but it would be quite asymmetric in brightness.
The ring is not wholly a direct image of the accretion disk. It includes light from all around the black hole that has been pulled into tight orbits at $\sim 1.5 r_s$ and then is bent into our line of sight. Some of that light may have executed more than one loop around the black hole. The presence of this "photon ring" is to some extent independent of the disk orientation.
What would be different though is light from the very inner part of the disk would be strongly Doppler boosted on the side coming towards us and the opposite going away from us. This should lead to a bright spot on one side of the black hole shadow.
The image below, taken from one of the recent EHT data release papers (Akiyama et al. 2022) shows an example (top right) of a model with an edge on disk. If you were to blur this to the the instrumental resolution of the Event Horizon Telescope, you would get an asymmetric ring.
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$\begingroup$ I respect you Sir as a good scientist, but this is not a good answer. It is one sided, uses unjustified specific assumptions, ignores the gravitational lensing shown in my comment above, mixes the frequency of radio waves with brightness of light, relies on the 3x3-pixel instrumental resolution of the EHT project, etc. $\endgroup$ Commented May 15, 2022 at 17:23
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$\begingroup$ @safesphere I have no idea what your comment about being one sided means. What are the two sides? The images shown are theoretical models of what would be seen for an edge-on disk with similar physical characteristics to that deduced to be around Sgr A*. Which is what the question asked for. It makes no assumption about the resolution of the instrument, since no instrumental resolution has been applied. Your comment (not an answer as usual) is a link and does not say anything about gravitational lensing, whereas my answer does. $\endgroup$– ProfRobCommented May 15, 2022 at 18:04
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$\begingroup$ @safesphere As regards mixing frequency and brightness I can only assume you are not aware that Doppler boosting increases the brightness of a source? $\endgroup$– ProfRobCommented May 15, 2022 at 18:07
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$\begingroup$ And what about as regards to everything else mentioned? ;) $\endgroup$ Commented May 16, 2022 at 3:29