Black holes have been discovered using several techniques, as outlined by How are black holes found?. What I was wondering is: are there automatic methods for locating them (e.g., artificial intelligence or image analysis techniques), or does the discovery still rely on actual people analyzing, e.g., the movement of stars in a certain portion of the space? For instance, I remember one of Andrea Ghez's talks and it looked to me that the analysis was performed manually.

Thank you in advance for your time.

  • $\begingroup$ Thank you, good point @ProfRob $\endgroup$ Aug 25, 2021 at 11:43
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    $\begingroup$ I would be specifically interested to find out whether the process of black holes discovery in the Milky Way (and perhaps in neighboring Milky Way galaxies) via optical lensing could be automated... $\endgroup$
    – Alex
    Aug 25, 2021 at 12:15
  • $\begingroup$ @Alex I think this is also interesting. My idea was to analyze image series taken at different times and to say, only based on the evolution showed there, if there is a black hole or not, for example because there are bodies orbiting around something that is invisible in the pictures at certain speeds and so on, but without necessarily writing full detailed equations that describe the motion laws hypothesized in case there is a black hole. $\endgroup$ Aug 25, 2021 at 12:42
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    $\begingroup$ Hi, you might want to un-accept the answer below, since you were asking about supermassive black holes, but the answer below is discussing methods for detecting stellar mass black holes, which are not necessarily the same methods. $\endgroup$ Aug 26, 2021 at 14:33
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    $\begingroup$ INdeed, methods for supermassive black holes exist and they are generally different, but with some overlap. Editing your question to make this clear might help to attract a more accurate answer. Your current question references Andrea Ghez, who works on supermassive black holes, but the answer you accepted is about general methods for detecting stellar mass black holes. The methods can be different generally because stellar mass and supermassive black holes tend to exist in different astrophysical circumstances/environments $\endgroup$ Aug 27, 2021 at 12:38

1 Answer 1


There are roughly three methods to "discover" black holes:

  1. Find the x-ray signature of their accretion disk.
  2. Discover the gravitational wave signature of black hole mergers.
  3. Be clever and find something new, such as the radial velocity measurements that discovered the "unicorn".

The processing of gravitational waves is almost entirely automatic. The measurements of stress that are made by Ligo and Virgo are automatically processed to look for evidence of a "chirp", and candidates are automatically flagged for further investigation. GW discoveries currently don't exactly locate the black hole, but does discover their existence and give information on mass and distance.

X-ray sources are automatically located by X-ray nova searches, with space telescopes. The telescope scans a region of the sky, looking for changes, and flags possible sources for further investigation. The hard work is in showing that a particular X-ray source is a black hole and not a neutron star or something else. This tends to involve gathering a combination of evidence rather than a single "discovery".

Other methods, such as the radial velocity can also be processed automatically (by automatic systems looking for exoplanets). These can discover candidates, but gathering the evidence that the signal is due to a black hole is a human task.

Many "black holes" are in reality "black hole candidates". There is evidence of something, and that is consistent with a black hole, and so rather than a "discovery", there is a process whereby other hypotheses are eliminated by further observations, until only the black hole hypothesis remains.

  • $\begingroup$ Thank you very much! This answer my question. Would you suggest any source to explore those techniques more in depth? $\endgroup$ Aug 25, 2021 at 12:47
  • $\begingroup$ IMHO, I would not call the method of gravitational waves capturing (in this case particular those which signal's match Einstein's mass predictions towards black hole(s) being the source of such gravitational waves) be termed as "discovery" (in the astronomical sense of this word) since this method doesn't has the capability to figure out the location of such black holes and their distance to the Earth. $\endgroup$
    – Alex
    Aug 25, 2021 at 13:44
  • $\begingroup$ @Alex You are mistaken. Look at any LIGO/Virgo paper about reported compact coalescing events and you'll see they measure the distance to the source from Earth and they constrain the region on the Earth's sky to locate the direction the signal came from. $\endgroup$ Aug 25, 2021 at 14:38
  • $\begingroup$ @Daddy Kropotkin This distance estimation and constraint of the region with regards to black hole location are too vague to call this to be an "astronomical discovery". Besides, this method is not based on a direct astronomical observation but rather on the indirect inference from the Einstein's theory. $\endgroup$
    – Alex
    Aug 25, 2021 at 14:57
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    $\begingroup$ This doesn’t cover various methods used to measure supermassive black holes, which is what the OP’s reference to “one of Andrea Ghez’s talks” is about. $\endgroup$ Aug 26, 2021 at 0:09

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