Astronomers Discover Three Supermassive Black Holes In A Single Distant Galaxy For The First Time Ever

An international team of astronomers has identified three actively feeding supermassive black holes within a single galaxy, marking the first time scientists have documented such a configuration in the distant universe and offering new clues about how the earliest, most massive black holes may have grown.

The discovery was made in the galaxy J0148-4214, located more than 12.5 billion light-years from Earth. Because the galaxy is so far away, its light has taken 12.5 billion years to reach Earth, meaning astronomers are observing it as it existed only about 1.2 billion years after the Big Bang. The research, led by the Max Planck Institute for Extraterrestrial Physics, was published in the journal Astronomy & Astrophysics.

Hannah Übler, a research group leader at the institute and lead author of the study, said the finding represents a milestone in the study of early black hole formation. “This is the first evidence of three active black holes in a single galaxy in the distant universe,” Übler said.

The three black holes vary considerably in both size and location within the galaxy. Two sit near the galactic center, separated from one another by roughly 620 light-years, while a third is positioned much farther out, approximately 5,500 light-years from the center. Using observations from the James Webb Space Telescope, researchers estimated the masses of the three black holes at roughly 80 million, 600,000 and 2 million times the mass of the sun, respectively.

Notably, the most massive of the three black holes is not the fastest-growing. According to the study, the smallest of the black holes, with a mass of roughly 600,000 suns, is accreting matter at a rate that actually exceeds the theoretical maximum predicted by standard models of black hole growth, a threshold known as the Eddington limit, while the larger, 80-million-solar-mass black hole is growing more slowly by comparison.

Researchers identified the three black holes by analyzing the spectral signatures of hydrogen gas moving at extremely high velocities within the galaxy, a pattern consistent with material orbiting close to a black hole’s gravitational field. Because the two central black holes were too close together to be visually distinguished as separate points of light, the team relied on a technique called spectro-astrometry, which measures subtle spatial shifts in the emitted light across the galaxy, to disentangle their individual signatures and confirm that two distinct sources, rather than one, were responsible for the observed spectral pattern.

Dr. Giovanni Mazzolari, a researcher at the Max Planck Institute and the study’s second author, said the depth of data provided by the James Webb Space Telescope made the full analysis possible. “The JWST data allowed us not only to identify the three black holes,” Mazzolari said, noting that the observations also allowed the team to estimate the black holes’ growth rates and the total stellar mass of their host galaxy, which the researchers calculated at approximately 1.3 billion solar masses.

The two central black holes are expected to merge within the next several hundred million years, according to the study’s dynamical estimates. Roberto Maiolino, a professor at the University of Cambridge and a co-author of the research, said the finding carries significant implications for understanding how the universe’s earliest supermassive black holes reached such enormous sizes so quickly. “These results are extremely exciting,” Maiolino said, adding that the findings suggest black hole mergers may represent an additional, faster pathway for rapid black hole growth in the early universe, alongside the more commonly studied process of direct gas accretion.

The origin of the third, more distant black hole remains less certain. Researchers said it could represent the leftover core of an earlier galactic merger, may have been displaced from the galactic center by a gravitational recoil following a previous black hole collision, or could simply be in the process of migrating inward toward the galaxy’s center over time.

The discovery adds direct observational support to existing theories of galaxy evolution, which hold that galaxies in the early universe frequently collided and merged with one another, a process that would have similarly driven the black holes at each galaxy’s center to merge and grow progressively larger over cosmic time. Scientists have said such mergers between supermassive black holes are expected to be a key source of the gravitational waves that future space-based observatories are designed to detect, making systems like J0148-4214 valuable natural laboratories for understanding how such mergers unfold.

Researchers emphasized that the discovery would likely not have been possible without the specific combination of spectroscopic and spatial data provided by the James Webb Space Telescope’s Near-Infrared Spectrograph integral field unit. Without that spatially resolved information, the team said, it is likely that only one of the three black holes in J0148-4214 would have been detected, with the other two remaining hidden within a single, blended spectral signature.

The findings are expected to inform future searches for similarly complex, multi-black-hole systems in other distant galaxies, as astronomers continue using the James Webb Space Telescope to probe the earliest chapters of black hole and galaxy formation in the universe’s history.