New Origin of Supermassive Black Holes Revealed by Supercomputer Simulation

Formation of Supermassive Stars

Artist’s impression of the formation of supermassive stars which evolve into a supermassive black hole. Credit: NAOJ

Computer simulations conducted by astrophysicists at Tohoku University in Japan, have revealed a new theory for the origin of supermassive black holes. In this theory, the precursors of supermassive black holes grow by swallowing up not only interstellar gas, but also smaller stars as well. This helps to explain the large number of supermassive black holes observed today.

Distribution of Matter Universe Simulation

Snapshots of the simulations showing the distribution of matter in the Universe at the time of black hole formation (top) and the density distribution of black hole-producing gas clouds (bottom). Credit: Sunmyon Chon

Almost every galaxy in the modern Universe has a supermassive black hole at its center. Their masses can sometimes reach up to 10 billion times the mass of the Sun. However, their origin is still one of the great mysteries of astronomy. A popular theory is the direct collapse model where primordial clouds of interstellar gas collapse under self-gravity to form supermassive stars which then evolve into supermassive black holes. But previous studies have shown that direct collapse only works with pristine gas consisting of only hydrogen and helium. Heavier elements such as carbon and oxygen change the gas dynamics, causing the collapsing gas to fragment into many smaller clouds which form small stars of their own, rather than a few supermassive stars. Direct collapse from pristine gas alone can’t explain the large number of supermassive black holes seen today.


The black dots represent massive stars and the white dots represent stars with small masses. While massive stars are formed in the center of the gas cloud, numerous smaller stars are also formed from the surrounding gas as it violently breaks up. Many of the smaller stars move with the flow of gas and merge with the massive stars. Credit: Sunmyon Chon

Sunmyon Chon, a postdoctoral fellow at the Japan Society for the Promotion of Science and Tohoku University and his team used the National Astronomical Observatory of Japan’s supercomputer “ATERUI II” to perform long-term 3D high-resolution simulations to test the possibility that supermassive stars could form even in heavy-element-enriched gas. Star formation in gas clouds including heavy elements has been difficult to simulate because of the computational cost of simulating the violent splitting of the gas, but advances in computing power, specifically the high calculation speed of “ATERUI II” commissioned in 2018, allowed the team to overcome this challenge. These new simulations make it possible to study the formation of stars from gas clouds in more detail.

Distribution of Matter Simulation

Snapshots of the simulations showing the density distribution of black hole-producing gas clouds. The black dots near the center of the figure represent massive stars, which are thought to evolve into a black hole in time. The white dots represent stars that are smaller than 10 solar mass and were formed by the fragmentation of the gas cloud. Many of the smaller stars merge with the supermassive stars at the center, allowing the massive stars to grow efficiently. Credit: Sunmyon Chon

Contrary to previous predictions, the research team found that supermassive stars can still form from heavy-element enriched gas clouds. As expected, the gas cloud breaks up violently and many smaller stars form. However, there is a strong gas flow towards the center of the cloud; the smaller stars are dragged by this flow and are swallowed-up by the massive stars in the center. The simulations resulted in the formation of a massive star 10,000 time more massive than the Sun. “This is the first time that we have shown the formation of such a large black hole precursor in clouds enriched in heavy-elements. We believe that the giant star thus formed will continue to grow and evolve into a giant black hole,” says Chon.

Mass Distribution of Stars Formed

Mass distribution of stars formed in the simulation of gas clouds containing heavy elements. In this research, the evolution of the first stars was calculated over roughly 10,000 years following their formation. The presence of heavy elements such as carbon and oxygen causes the gas cloud to break up violently, resulting in a distribution with a peak around one solar mass. On the other hand, a supermassive star 10,000 times the mass of the Sun would also form at the same time. It is thought that the supermassive stars will grow further in mass and eventually evolve into a supermassive black hole. Credit: Sunmyon Chon

This new model shows that not only primordial gas, but also gas containing heavy elements can form giant stars, which are the seeds of black holes. “Our new model is able to explain the origin of more black holes than the previous studies, and this result leads to a unified understanding of the origin of supermassive black holes,” says Kazuyuki Omukai, a professor at Tohoku University.

This result was published as Chon and Omukai “Supermassive star formation via super competitive accretion in slightly metal-enriched clouds” in Monthly Notices of the Royal Astronomical Society in May 2020.

NAOJ Supercomputer ATERUI II Cray XC50

NAOJ supercomputer ATERUI II (Cray XC50) operated at NAOJ Mizusawa Campus (Oshu, Iwate) with a theoretical peak performance of 3.087 Pflops. Credit: NAOJ

This research utilized the NAOJ supercomputer ATERUI II (Cray XC50) for the simulation of massive star formation. ATERUI II is operated at NAOJ Mizusawa Campus (Oshu, Iwate) with a theoretical peak performance of 3.087 Pflops.

Reference: ” Supermassive star formation via super competitive accretion in slightly metal-enriched clouds” by Sunmyon Chon and Kazuyuki Omukai, 4 April 2020, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/staa863

4 Comments on "New Origin of Supermassive Black Holes Revealed by Supercomputer Simulation"

  1. I have always held a spot in my heart for direct hydrogen gas to black hole formation to explain SMBH’s. Sigh, fondness of an idea does not mean standing up under rigorous proof.
    The math says not enough time for the percentage of mass in black holes versus the time of existence before contamination became too great to continue.
    All the really giant SMBH’s (10,000,000,000+) are likely the direct condensation, but that is a small enough percent of a percent be interesting without being a fundamental building block of the universe.

    The very high rate of formation and the density of black holes withing the gas clouds combine to create the majority of black holes from 10,000 through 10,000,000 solar masses.
    Those black holes with 10,000,000,000 solar mass and larger are direct formation results. In between is a combination of the methods.

    Now to wait for the Webb telescope to be orbited. Hopefully all of this will not be turned on its head by new data.

    That is my take on this article, but I am woefully under educated on the subject.

  2. Harry L Bowman | June 20, 2020 at 2:43 pm | Reply

    Isn’t a star that size going to disperse through radiation pressure?

  3. As much as I appreciate all scientific enquiry, this just seems like another ‘Japan discovers why stirring tea causes a mini whirlpool!’ story. Do we really need a computer model to explain this stuff? and can we really call something this obvious and physically observed numerous times by numerous telescopes a discovery?

    • Ross, I am not sure what you mean by “another ‘Japan discovers why stirring tea causes a mini whirlpool!’ story”. Perhaps you are unaware of an important paper published by A. Einstein in 1926 that refers in some detail to the scientific problem of the circulation of tea in a cup when it is stirred
      .
      On the other hand, if you have another research paper in mind, perhaps you would be so kind as to cite it for your readers.

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