New Research Sheds Light On Black Hole Growth

Article written: 13 Feb , 2013
Updated: 23 Dec , 2015

In a new study led by University of Central Lancashire astronomer Dr. Victor Debattista, researchers are looking into the mystery of how black holes grow and evolve. For many years, astronomers surmised black holes took on mass when their host galaxies merged, but now new modeling techniques show that black holes in spiral galaxies are forced to take on mass.

“Recent Hubble Space Telescope (HST) observations have revealed that a majority of active galactic nuclei (AGN) are resident in isolated disk galaxies, contrary to the usual expectation that AGN are triggered by mergers.” says Debattista. “Here we develop a new test of the cosmic evolution of supermassive black holes (SMBHs) in disk galaxies by considering the local population of SMBHs. We show that substantial SMBH growth in spiral galaxies is required as disks assemble.”

Weighing in a range of one million to one billion times that of the Sun, the black holes located at the core of most galaxies would appear to be gaining at much quicker rates than expected. These are not just exceptions – more like rules. Even the Milky Way’s quiescent black hole might be gaining as much mass as the Sun every 3,000 years. Past observations have shown growth during collision events, when huge amounts of gas around the black hole become intensely hot and shine as an active galactic nucleus. This is a process which can be spotted as far back as the first formations in our Universe. However, these new simulations are giving insight into large scale growth without the need for violence.

“The X-ray-selected sample of moderate luminosity AGN consists of more than 50% disk galaxies, with ongoing mergers evident no more frequently than in nonactive galaxies.” explains the research team. “Some show that even heavily obscured quasars are hosted largely by disks, not by mergers. Studies of star-formation using Herschel find that the specific star formation rates of X-ray selected AGN hosts are no different from those of inactive galaxies, also indicating that AGN hosts are not undergoing fundamentally different behaviors”

These modeling techniques, combined with current observations done with the Hubble Space Telescope, give credence to the theory that black holes can gain significant mass even in “quiet” spiral galaxies. As a matter of fact, there is a strong possibility that AGNs present in some spiral galaxies may even outnumber galaxy mergers. To make this concept even more exciting, astronomers are anticipating an event later this year in our own galaxy – an event where a gas cloud near the Milky Way’s nucleus will encounter our own central black hole. According to predictions, our black hole may take on as much as 15 Earth masses in a period of 10 years from this cloud.

This concept of black hole growth isn’t entirely new, though. According to other research done with the Hubble Space Telescope and led by Dr. Stelios Kazantzidis of Ohio State University and Professor Frank C. van den Bosch of Yale University, they had previously pinpointed mass properties of black holes – making size predictions which utilized the speed of stars residing in the galaxies. In this instance, the team disproved previous assumptions that black holes were unable to grow while the host galaxy grew. Their comparison of spiral and elliptical galaxies “found there is no mismatch between how big their black holes are.” This means black holes would be gaining in mass – growing along at the same rate as the galaxy itself.

“These simulations show that it is no longer possible to argue that black holes in spiral galaxies do not grow efficiently. ” comments Debattista on this new research. ” Our simulations will allow us to refine our understanding of how black holes grew in different types of galaxies.”

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10 Responses

  1. There has to be a point that the fusion of subatomic particles reach such high energy levels that it is able to rip these black holes a part. I just don’t want to be in the first galaxy when that happens.

  2. Member

    Can a black hole galactic nucleus eventually swallow up every single star or remnant in the same galaxy it dwells in?

    • Lenard Lindstrom says

      I don’t see how that could happen. A lot of energy keeps a star in orbit within a galaxy, and so away from the central black hole. To fall inward, that energy has to be transferred to something else, like another star, or galactic gas and dust, which will then move outward. So for some part of a galaxy to be swallowed, another part has to be tossed away.

  3. Chetan Chauhan says

    “To make this concept even more exciting, astronomers are anticipating an event later this year in our own galaxy – an event where a gas cloud near the Milky Way’s nucleus will encounter our own central black hole.”

    Don’t forget that the galaxy black hole is abt 25,000 light years from the Earth. Which means the gas cloud near the galaxy center has already been digested by Sagittarius A* , and what we will see soon is the after effects of what had already happened about 25,000 years ago.

    • Also don’t forget that astronomers observe local observation time, and don’t do double accounting.

    • lcrowell says

      In some ways that may be the case. However this is probably only the case for quantum black holes that are smaller than a nucleus. These galactic black holes are thundering behemoths, and they will exist for 10^{100} years or so. They will eventually decay by Hawking radiation, but for all practical purposes they are “eternal,” and there is no process in the known universe that can “digest them” away.

      There is I think a fundamental vacuum state that involves a large set of symmetries. This is a sporadic group, where I will just say is a large set of symmetries that define a vacuum. However, this theory is cubic which means there are 3 sets of vacua, where on only one of them do you have this vast set of symmetries. This vacua sits on the top of a potential “hill” and is not stable. The other two vacua sit on valleys and are given by different broken symmetry conditions on this large set of symmetries. One of these broken set of symmetries describes free particles or strings in space and is analogous to the superconductivity state. The other describes a condensate state of particles or strings, where this is analogous to a Mott insulating state. This last broken symmetry state is a black hole. The unstable vacuum state with complete symmetry is at the peak of a potential hill separating these two valleys of broken symmetry. Quantum mechanically states in one valley can tunnel through the hill and enter the other valley. In this way a black hole can quantum mechanically decay, or particles outside have some probability of entering the black hole.

      For this system a black hole in its vacuum states at the bottom of the condensate valley could be given a lot of energy so these states are bumped to the top of that hill or higher. This would be a case where the black hole is “demolished.” However, it must be remembered that his works for quantum black holes. The amount of energy required to destroy a black hole at the center of a galaxy would be equivalent to billions of galactic mass-energy equivalents. It can’t happen for practical reasons. In effect the condition for this demolition only existed with the quantum cosmology and the inflationary phase of the universe.


      • Member
        Aqua4U says

        Always well spoken and insightful. Your comments are well beyond thought provoking and into the realm of infinite consciousness, where we leave behind the known limitations of space and time and are tempted to dwell in the truth of the multiple realities where the quantum and macro scale symbiosis of being is revealed. My angels told me to say that and also to encourage you onward!

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