Simulation of globular cluster formation. Individual blue-white stars can be seen. The “cloud” around them is interstellar gas. The gas color gradation shows cooler (dark) and warmer (bright) regions. Credit: Michiko Fujii and Takaaki Takeda. 2024 Download image (3.7MB)
The first star-by-star simulations of globular cluster formation show that massive star collisions can start a runaway process resulting in the formation of intermediate-mass black holes. These results can help explain the origins of this rare type of black holes.
Known black holes generally fall into two categories; low mass black holes with dozens of times the mass of the Sun and high mass black holes with masses more than tens-of-thousands of times that of the Sun. However, black holes with masses in between those two are rarely found, and are considered a major mystery in the evolution of black holes.
One possible place to look for intermediate-mass black holes is in globular clusters, self-contained globs of stars in the halo around the Milky Way Galaxy. One of the hypotheses for the formation of black holes in globular clusters is a “runaway collision” of stars in forming star clusters embedded in their parental molecular clouds. To confirm this theory, however, simulations that reproduce the motion of individual stars inside molecular clouds are needed, but have not been possible due to problems with computational techniques and computer capabilities. Previous simulations of globular cluster evolution have reduced computing costs by bundling stars into groups to track their motion. But these simulations could not reproduce runaway collisions.
A team led by Michiko S. Fujii at The University of Tokyo tested a new recipe for intermediate black holes using the world’s most powerful supercomputer dedicated to astronomy, ATERUI II at the National Astronomical Observatory of Japan. Their new simulation code and the performance of ATERUI II have enabled the world’s first simulation of the formation of individual stars in globular clusters, accurately reproducing the motion of more than one million stars in the interstellar gas, including their collisions and mergers, without eating up unrealistic amounts of computing time.
The results of the simulation show that runaway collisions of stars occur in the cluster during its formation, eventually forming a massive star with a mass about 10,000 times that of the Sun. Calculations based on stellar evolution theory predict that the massive star would become an intermediate-mass black hole with a mass three to four thousand times that of the Sun. This result provides strong theoretical support for the existence of intermediate-mass black holes in globular clusters.
The first star-by-star simulations of globular cluster formation show that massive star collisions can start a runaway process resulting in the formation of intermediate-mass black holes. These results can help explain the origins of this rare type of black holes.
Known black holes generally fall into two categories; low mass black holes with dozens of times the mass of the Sun and high mass black holes with masses more than tens-of-thousands of times that of the Sun. However, black holes with masses in between those two are rarely found, and are considered a major mystery in the evolution of black holes.
One possible place to look for intermediate-mass black holes is in globular clusters, self-contained globs of stars in the halo around the Milky Way Galaxy. One of the hypotheses for the formation of black holes in globular clusters is a “runaway collision” of stars in forming star clusters embedded in their parental molecular clouds. To confirm this theory, however, simulations that reproduce the motion of individual stars inside molecular clouds are needed, but have not been possible due to problems with computational techniques and computer capabilities. Previous simulations of globular cluster evolution have reduced computing costs by bundling stars into groups to track their motion. But these simulations could not reproduce runaway collisions.
A team led by Michiko S. Fujii at The University of Tokyo tested a new recipe for intermediate black holes using the world’s most powerful supercomputer dedicated to astronomy, ATERUI II at the National Astronomical Observatory of Japan. Their new simulation code and the performance of ATERUI II have enabled the world’s first simulation of the formation of individual stars in globular clusters, accurately reproducing the motion of more than one million stars in the interstellar gas, including their collisions and mergers, without eating up unrealistic amounts of computing time.
The results of the simulation show that runaway collisions of stars occur in the cluster during its formation, eventually forming a massive star with a mass about 10,000 times that of the Sun. Calculations based on stellar evolution theory predict that the massive star would become an intermediate-mass black hole with a mass three to four thousand times that of the Sun. This result provides strong theoretical support for the existence of intermediate-mass black holes in globular clusters.
Detailed Article(s)
Medium and mighty: intermediate-mass black holes can survive in globular clusters
The University of Tokyo
Release Information
Researcher(s) Involved in this Release:
Michiko S. Fujii (Department of Astronomy, Graduate School of Science, The University of Tokyo)
Ataru Tanikawa (Center for Information Science, Fukui Prefectural University)
Yutaka Hirai (Astronomical Institute, Tohoku University)
Takayuki Saitoh (Department of Planetology, Graduate School of Science, Kobe University)
Coordinated Release Organization(s):
The University of Tokyo
Fukui Prefectural University
Tohoku University
Kobe University
National Astronomical Observatory of Japan
Paper(s):
Michiko S. Fujii et al. “Simulations predict intermediate-mass black hole formation in globular clusters”, in Science, DOI: 10.1126/science.adi4211
