Deepening Mystery: Astronomers on the Hunt for a Missing Supermassive Black Hole [Video]

Disc of Material Circling a Supermassive Black Hole

Artist’s impression of  a disc of material circling a supermassive black hole. Credit: ESA/Hubble, M. Kornmesser

The mystery surrounding the whereabouts of a supermassive black hole has deepened.

Despite searching with NASA’s Chandra X-ray Observatory and Hubble Space Telescope, astronomers have no evidence that a distant black hole estimated to weigh between 3 billion and one hundred billion times the mass of the Sun is anywhere to be found. This missing black hole should be in the enormous galaxy in the center of the galaxy cluster Abell 2261, which is located about 2.7 billion light years from Earth.

Nearly all large galaxies contain a supermassive black hole, with a mass that is millions or billions of times that of the sun in their centers. Since the mass of a central black hole usually tracks with the mass of the galaxy itself, astronomers expect the galaxy in the center of Abell 2261 contains a supermassive black hole that rivals the heft of some of the largest known black holes in the Universe.

Such black holes are usually found in the centers of galaxies. Using Chandra data obtained in 1999 and 2004, astronomers had already searched the center of Abell 2261’s large central galaxy for signs of a supermassive black hole. They looked for material that has been superheated as it fell towards the black hole and produced X-rays, but did not detect such a source.

In 2018, a team of scientists used Chandra to get new, longer observations obtained in 2018 of Abell 2261. They also considered an alternative explanation: what if the black hole was ejected from the host galaxy’s center? During a merger of two galaxies, which likely happened in the past to form Abell 2261, the central black holes in each galaxy could have merged to form one enormous black hole. This violent event would have also generated a huge amount of gravitational waves. If the gravitational waves were stronger in one direction than another, theory predicts that the new, even more massive black hole would have been sent careening away from the center of the galaxy in the opposite direction. This is called a recoiling black hole.

Astronomers have not found definitive evidence for recoiling black holes and they do not know whether supermassive black holes even get close enough to each other to produce gravitational waves and merge. The detection of recoiling supermassive black holes would embolden scientists using and developing observatories to detect gravitational waves from merging supermassive black holes.

The mystery of this titanic-sized black hole in Abell 2261 therefore continues. Although this latest search was unsuccessful, hope remains for astronomers looking for this supermassive black hole in the future. Once the James Webb Space Telescope launches, astronomers should be able to use its capabilities to join with Chandra’s and others to look at Abell 2261 and others like it.

Read Deepening Astronomical Mystery: On the Hunt for a Missing Giant Black Hole for more on this research.

Reference: “Chandra Observations of Abell 2261 Brightest Cluster Galaxy, a Candidate Host to a Recoiling Black Hole” by Kayhan Gültekin, Sarah Burke-Spolaor, Tod R. Lauer, T. Joseph W. Lazio, Leonidas A. Moustakas, Patrick Ogle and Marc Postman, 5 January 2021, The Astrophysical Journal.
DOI: 10.3847/1538-4357/abc483

9 Comments on "Deepening Mystery: Astronomers on the Hunt for a Missing Supermassive Black Hole [Video]"

  1. The Abell 2261 galaxy center is not a black hole yet.
    It’s a black globe yet.
    There will be a black hole in the future.
    Therefore it does not appear.

    Sorry for my insufficient english.

    • Torbjörn Larsson | February 1, 2021 at 12:57 pm | Reply

      “Nearly all large galaxies contain a supermassive black hole, with a mass that is millions or billions of times that of the sun in their centers.”

      That covers large galaxies near us, where we see them as they recently were, but also very distant which shows these supermassive black holes have been associated with galaxies throughout history of large galaxies (which is almost all the way back in time to the hot big bang).

      Your English is sufficient, though I must admit that I don’t understand what “a black globe” is. A “black hole” is an accepted astronomical term, but I haven’t seen that other term of yours.

  2. What happens when two black holes merge? If time slows infinity at the event horizon how can they actually combine. And if they do how can the matter within the event horizon move to form a new spherical shape. And does it oscillate with the aftershock,? Would a supermassive black hole ring like an enormous bell?

    • Torbjörn Larsson | February 1, 2021 at 1:26 pm | Reply

      – If time slows infinity at the event horizon how can they actually combine.”

      Relativity is how nature maintain the same physics laws for all “observers” but at the cost of such effects as length contraction and time dilation as seen for some observers but not others. Up to the point that different observers can see different time ordering in some cases, yet agree that their observations agree with shared phsyics laws. So I wouldn’t worry about how time looks for observers at the event horizon – and in fact black hole physics ultimately refer to what observers at an “infinite” distance would see.

      “To a distant observer, clocks near a black hole would appear to tick more slowly than those further away from the black hole.[84] Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow as it approaches the event horizon, taking an infinite time to reach it.[85] At the same time, all processes on this object slow down, from the view point of a fixed outside observer, causing any light emitted by the object to appear redder and dimmer, an effect known as gravitational redshift.[86] Eventually, the falling object fades away until it can no longer be seen. Typically this process happens very rapidly with an object disappearing from view within less than a second.[87]

      On the other hand, indestructible observers falling into a black hole do not notice any of these effects as they cross the event horizon. According to their own clocks, which appear to them to tick normally, they cross the event horizon after a finite time without noting any singular behaviour; in classical general relativity, it is impossible to determine the location of the event horizon from local observations, due to Einstein’s equivalence principle.[88][89]”

      [“Black hole” @ Wikipedia]

      – “And if they do how can the matter within the event horizon move to form a new spherical shape.”

      There isn’t any matter as such in general relativity descriptions of black holes – which is where they appear – and from the outside all we see is a black hole mass, linear momentum (movement against other objects). angumar momentum (rotation), electric charge and temperature (from event horizon thermal radiation).

      [“Black hole” @ Wikipedia]

      But all static – merged – black holes have a general relativistic solution predicting them. The simplest solution is for a non-rotating, non-charged black hole and it is perfectly spherical.

      [“Schwarzschild metric” @ Wikipedia]

      It is perhaps a bit non-intuitive since a collapse that we see around here is often compressional mechanically generated, and it turns out when you heat matter you get instabilities from the hotter inside trying to push back. So we never see a “perfect” collapse. (C.f. how hard it is to make fusion in laser fusion compression facilities.)

      But gravity is thermodynamically different, since gravitationally bound systems have negative specific heat – the system is heated up under contraction but obviously its energy is going down (closer masses) and not up.

      That is why we see meteorites burn as they descend the atmosphere.

      And that is why it is practically impossible to avoid sphericity under gravitational collapse such as resulting in a black hole. It wasn’t until recently that physicists managed to show that a 3D simulation of a collapsing star can sometimes generate sufficient turbulence to result in a supernova instead.

      – “And does it oscillate with the aftershock,? Would a supermassive black hole ring like an enormous bell?”


      The first stage of the life of a binary black hole is the inspiral, a gradually shrinking orbit. The first stages of the inspiral take a very long time, as the gravitation waves emitted are very weak when the black holes are distant from each other. In addition to the orbit shrinking due to the emission of gravitational waves, extra angular momentum may be lost due to interactions with other matter present, such as other stars.

      As the black holes’ orbit shrinks, the speed increases, and gravitational wave emission increases. When the black holes are close the gravitational waves cause the orbit to shrink rapidly.

      The last stable orbit or innermost stable circular orbit (ISCO) is the innermost complete orbit before the transition from inspiral to merger.

      This is followed by a plunging orbit in which the two black holes meet, followed by the merger. Gravitational wave emission peaks at this time.

      Immediately following the merger, the now single black hole will “ring”. This ringing is damped in the next stage, called the ringdown, by the emission of gravitational waves. The ringdown phase starts when the black holes approach each other within the photon sphere. In this region most of the emitted gravitational waves go towards the event horizon, and the amplitude of those escaping reduces. Remotely detected gravitational waves have a fast reducing oscillation, as echos of the merger event result from tighter and tighter spirals around the resulting black hole.”

      [“Binary black hole” @ Wikipedia]

      • I find your explanations thought provoking. While I have no education in these matters, I would still like to know;
        If from a distance clocks crossing into a Black Hole would appear to slow down so noticably to the distant viewers, yet, the same clock wouldn’t appear to have slowed down to the travelers with the clock. Question:
        If so, could not the slowing of the clock to the distant viewers, be a sort of optical illusion,caused perhaps by say gravitational influences, if not a combination of influences, such as some of those you mentioned above? Could not those influences distort what,not only what the distant observers see, but all things measured and such from such distances? As an uneducated person, I apologize if my question is, well, ignorant, for lack of a better term. If you could be kind enough to E-mail me any thoughts or info, I’d be grateful.

  3. Aafreen Shaikh | January 31, 2021 at 9:36 pm | Reply

    It’s beyond our thinking what the almighty created turn to that creator who made these heavenly bodies turn to the creator who is allowing us to explore his creation truly he is all knowing and the most merciful… Think about his creation how beautiful it is and think how beautiful he( the creator ) must be … All praises are to the lord of this beautiful universe…

  4. Gunnar Garisson | February 1, 2021 at 3:58 pm | Reply

    It was delicious.

  5. Bibhutibhusanpàtel | February 2, 2021 at 8:58 am | Reply


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