Mysterious Flickering Decoded: Supermassive Black Hole Size Revealed by Its Feeding Pattern

Accretion Disk Rotating Around Supermassive Black Hole

An artist’s impression of an accretion disk rotating around an unseen supermassive black hole. The accretion process produces random fluctuations in luminosity from the disk over time, a pattern found to be related to the mass of the black hole in a new study led by University of Illinois Urbana-Champaign researchers. Credit: Graphic courtesy Mark A. Garlick/Simons Foundation

The feeding patterns of black holes offer insight into their size, researchers report. A new study revealed that the flickering in the brightness observed in actively feeding supermassive black holes is related to their mass.

Supermassive black holes are millions to billions of times more massive than the sun and usually reside at the center of massive galaxies. When dormant and not feeding on the gas and stars surrounding them, SMBHs emit very little light; the only way astronomers can detect them is through their gravitational influences on stars and gas in their vicinity. However, in the early universe, when SMBHs were rapidly growing, they were actively feeding – or accreting – materials at intensive rates and emitting an enormous amount of radiation – sometimes outshining the entire galaxy in which they reside, the researchers said.  

The new study, led by the University of Illinois Urbana-Champaign astronomy graduate student Colin Burke and professor Yue Shen, uncovered a definitive relationship between the mass of actively feeding SMBHs and the characteristic timescale in the light-flickering pattern. The findings are published in the journal Science.

The observed light from an accreting SMBH is not constant. Due to physical processes that are not yet understood, it displays a ubiquitous flickering over timescales ranging from hours to decades. “There have been many studies that explored possible relations of the observed flickering and the mass of the SMBH, but the results have been inconclusive and sometimes controversial,” Burke said.

The team compiled a large data set of actively feeding SMBHs to study the variability pattern of flickering. They identified a characteristic timescale, over which the pattern changes, that tightly correlates with the mass of the SMBH. The researchers then compared the results with accreting white dwarfs, the remnants of stars like our sun, and found that the same timescale-mass relation holds, even though white dwarfs are millions to billions times less massive than SMBHs.

The light flickers are random fluctuations in a black hole’s feeding process, the researchers said. Astronomers can quantify this flickering pattern by measuring the power of the variability as a function of timescales. For accreting SMBHs, the variability pattern changes from short timescales to long timescales. This transition of variability pattern happens at a characteristic timescale that is longer for more massive black holes.

The team compared black hole feeding to our eating or drinking activity by equating this transition to a human belch. Babies frequently burp while drinking milk, while adults can hold in the burp for a more extended amount of time. Black holes kind of do the same thing while feeding, they said.

“These results suggest that the processes driving the flickering during accretion are universal, whether the central object is a supermassive black hole or a much more lightweight white dwarf,” Shen said.

“The firm establishment of a connection between the observed light flicker and fundamental properties of the accretor will certainly help us better understand accretion processes,” said Yan-Fei Jiang, a researcher at the Flatiron Institute and study co-author.

Astrophysical black holes come in a broad spectrum of mass and size. In between the population of stellar-mass black holes, which weigh less than several tens of times the mass of the sun, and SMBHs, there is a population of black holes called intermediate-mass black holes that weigh between about 100 and 100,000 times the mass of the sun.

IMBHs are expected to form in large numbers throughout the history of the universe, and they may provide the seeds necessary to grow into SMBHs later. However, observationally this population of IMBHs is surprisingly elusive. There is only one indisputably confirmed IMBH that weighs about 150 times the mass of the sun. But that IMBH was serendipitously discovered by the gravitational wave radiation from the coalescence of two less-massive black holes.

“Now that there is a correlation between the flickering pattern and the mass of the central accreting object, we can use it to predict what the flickering signal from an IMBH might look like,” Burke said.

Astronomers worldwide are waiting for the official kickoff of an era of massive surveys that monitor the dynamic and variable sky. The Vera C. Rubin Observatory in Chile’s Legacy Survey of Space and Time will survey the sky over a decade and collect light flickering data for billions of objects, starting in late 2023.

“Mining the LSST data set to search for flickering patterns that are consistent with accreting IMBHs has the potential to discover and fully understand this long-sought mysterious population of black holes,” said co-author Xin Liu, an astronomy professor at the U. of I.

Reference: “A characteristic optical variability timescale in astrophysical accretion disks” by Colin J. Burke, Yue Shen, Omer Blaes, Charles F. Gammie, Keith Horne, Yan-Fei Jiang, Xin Liu, Ian M. McHardy, Christopher W. Morgan, Simone Scaringi and Qian Yang, 12 August 2021, Science.
DOI: 10.1126/science.abg9933

This study is a collaboration with astronomy and physics professor Charles Gammie and astronomy postdoctoral researcher Qian Yang, the Illinois Center for Advanced Study of the Universe, and researchers at the University of California, Santa Barbara; the University of St. Andrews, U.K.; the Flatiron Institute; the University of Southampton, U.K.; the United States Naval Academy; and the University of Durham, U.K.

Burke, Shen, and Liu also are affiliated with the Center for Astrophysical Surveys at the National Center for Supercomputing Applications at Illinois.

The National Science Foundation, the Science and Technology Facilities Council, and the Illinois Graduate Survey Science Fellowship supported this research.

7 Comments on "Mysterious Flickering Decoded: Supermassive Black Hole Size Revealed by Its Feeding Pattern"

  1. BibhutibhusanPatel | August 12, 2021 at 2:33 pm | Reply

    The Authors are right in their approch that typical scale flickering of brightness of each accerting SMBH due to feeding is directly proportional to respective mass.This ŕelates to space-time for any SMBH singularity.But this is a
    relative view needs more studies for specialisation.

  2. LOL The Milky Way Galaxy is an “accretion disk” in its adolescence. But we are “on the table/menu” as it were. It is only a matter of TIME… which we measure in days-to-years-to-millennia, HERE, on a miniscule Rock that spins at the Speed of Sound, on the outer “banks” of a spiral Galaxy. PROXIMITY AND SCALE… TIME AND DISTANCE… “It” all depends on how one looks at it; Which Is To Say (WITS): Wisdom is a RELATIVE term. Science is relative WISDOM.

    • Torbjörn Larsson | August 15, 2021 at 4:36 am | Reply

      Why the crackpot shouting/”bold” font?

      Science is absolute on facts and well tested theories, which is why we have one global science and not splinter national such.

  3. BibhutibhusanPatel | August 13, 2021 at 12:23 am | Reply

    This phenomena or theory ìs not at all new.We had already an analysis for suçh optical waves are confìrming theory of relativìty,while light is bending back òf SMBH.ĺn seqùence of dìscoveries we are relatìng the pattern òf light emitted from SMBH,that ĺeft since last dìscòvery mentioned.Goòd to get specify galactic ròtatiòn by a qùantity chaŕacterstic time period of ffĺìckerìng brìghtness òf light at accretion dìsc òf SMBH.Staŕs folĺowìng SMBH sìnģuĺarity in Space-Tìme is fìne ìn all gaĺaxìes.Thanks & còngratulations tò the aùthòrs for òbservations abĺe to draw rìght cònclusion.

    • Torbjörn Larsson | August 15, 2021 at 4:42 am | Reply

      Please read the paper before commenting. The flicker proxy for mass is independent of relativity or spacetime of black holes. [Even if the flicker mechanisms may not be.]

      And it is all new, according to the press release that I must guess you didn’t read either (or in full) – so we can add that to your “do this before commenting” practice list:

      ““There have been many studies that explored possible relations of the observed flickering and the mass of the SMBH, but the results have been inconclusive and sometimes controversial,” Burke said.”

  4. Torbjörn Larsson | August 15, 2021 at 4:33 am | Reply

    These results are cool and useful!

    One can see that in the figure 1 of preprint [repeated here for convenience: ]. I don’t think they integrated the whide dwarf results to a complete statistical model, but the the blue line suggest that the mass slope would pivot closer to 0.5 which is pretty much a proxy for the linear scale of the emission region.

    “This timescale is consistent with the expected thermal timescale at the UV-emitting radius in standard accretion disk theory.”

    They cannot exclude other timescales, but accepting the thermal timescale they think their flicker data spectral and time behavior may be explained by variability in the inner part of the accretion disk which UV emission damping timescale is shared with other emission.

  5. SPACEANDBEYOND | May 20, 2022 at 11:59 pm | Reply


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