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Three colliding galaxies captured by the Hubble Space Telescope. The merger of three galaxies, each containing a supermassive black hole, could be the origin of the rare supermassive black holes, the heaviest objects in the universe. Photo: NASA
Theѕe сolossal сosmiс entіtіes, wіth mаsses exсeeding 10 bіllіon tіmes thаt of the Sun, hаve іntrіgued аstronomers due to theіr іmmense ѕize аnd enіgmatіc behаvior.In comparison to the supermassive black holes commonly found at the centers of galaxies, such as in the Milky Way, these universe-spanning giants appear even more fearsome. Their immense dimensions have posed a challenge for astronomers to comprehend.
Now, a study involving a rare galaxy merger containing three supermassive black holes at its core has provided insights that shed light on the origins of these cosmic behemoths. Leveraging high-resolution universe simulation technology known as ASTRID, a research team from the Harvard-Smithsonian Center for Astrophysics has modeled the evolution of the universe about 11 billion years ago.
Through their simulation, the team witnessed the birth of a supermassive black hole resulting from the merger of three galaxies. Each of these galaxies contained its own stellar nucleus, a supermassive black hole that consumed matter and powered immense radiation bursts, potentially outshining all stars in their host galaxies combined.
Upon the convergence of the stellar triad, they coalesced into an even larger supermassive black hole, initiating an accretion process that allowed the combined object to reach a state of supermassive magnitude.
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Supercomputer simulations depict three galaxies with supermassive black holes at their centers merging into a galaxy with a supermassive black hole at its core. Photo: Yueying Ni
“This system includes three bright quasars powered by supermassive black holes, each galaxy residing in large galaxies about 10 times the mass of our Milky Way,” added Yueying Ni.
The research group’s simulation model indicates that the stellar triad is capable of merging over a span of 150 million years, giving rise to the largest black hole in the entire simulation, with a mass exceeding 300 billion times that of the Sun. In other words, this supermassive black hole is larger than the combined mass of all stars in the Milky Way. The rarity of triple quasar systems may help explain why supermassive black holes in the actual universe are so challenging to capture.
“While we generally expect larger systems to contain more massive black holes, supermassive black holes are challenging to capture because their growth is a self-regulated process. In an isolated system/galaxy, when a black hole grows large enough, it produces strong feedback to its surrounding environment and limits itself from growing too rapidly,” Ni explained.
In essence, astronomers hope that the formation of a supermassive black hole with masses even at the lower end of the spectrum (around 10 billion times the mass of the Sun) only occurs in exceedingly rare and extreme situations. In this case, it occurs through a repetitive merging process of three large galaxies.
The research team’s future plans involve statistically analyzing multiple stellar triad systems within the ASTRID simulation to study the properties of their host galaxies. By conducting simulated observations and monitoring how supermassive black holes and host galaxies develop in the simulation, they aim to gain a better understanding of these processes.