Astronomers Baffled by 3 Feeding Supermassive Black Holes Packed Into Early Galaxy When the Universe Was Barely a Billion Years Old

Illustration by ZME Science.

Astronomers using the James Webb Space Telescope say that a super distant galaxy appears to contain not one growing black hole, but three — all actively feeding on surrounding matter. Two sit remarkably close together near the galaxy’s center. A third lurks farther out, with an uncertain past and an even less certain future.

The light from the galaxy in question, known as J0148-4214, has traveled for roughly 12.5 billion years, meaning astronomers see the galaxy as it existed only about 1.15 billion years after the Big Bang. The three black holes range from roughly 600,000 to 80 million times the mass of the Sun. If the interpretation holds, this is the earliest known example of three actively accreting black holes packed into one galactic system. Typically, galaxies have a single supermassive black hole at their galactic core, which gravitationally tethers the stars that form the galaxy.

“This is the first evidence of three active black holes in a single galaxy in the distant universe,” Hannah Übler, an astronomer at the Max Planck Institute for Extraterrestrial Physics and lead author of the new Astronomy & Astrophysics study, said in a Max Planck Institute press release.

The discovery could help address one of the persistent puzzles raised by JWST, which is currently humanity’s most sensitive instrument for observing objects from the early universe: how black holes became so massive so early. Gas can feed them, sometimes extraordinarily quickly. But J0148-4214 offers unusually direct evidence for another route — multiple black holes growing by finding and eventually swallowing one another.

Map of the distant galaxy J0148-4214 in ionised hydrogen (Hα). The locations of the three massive black holes are indicated by black circles (not to scale). The most massive and least massive black holes are located in the galaxy centre; a third black hole is located in the galaxy outskirts. Credit: Hannah Übler

Astronomers had actually noticed J0148-4214 before. Earlier JWST observations identified it as a galaxy containing a single active black hole. In December 2024, Übler’s team returned with NIRSpec, Webb’s near-infrared spectrograph, using a mode that records a spectrum at many positions across the galaxy rather than blending the whole object into one measurement.

That spatial information changed the picture completely.

Astronomers cannot see the black holes themselves. Instead, they looked for gas moving at extreme speeds around them.

At the galaxy’s center, Webb detected hydrogen gas with two distinct patterns of motion, suggesting two separate feeding black holes packed into the same small region. A third similar signal appeared about 5,500 light-years away.

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The two central black holes are so close that Webb cannot resolve them as separate points of light. But by tracking where different parts of the hydrogen signal came from, the researchers found that the two sources were offset by about 620 light-years — far too widely separated to belong to a single black hole.

“The fingerprints look like black holes and the ‘shape’ is best explained with two separate ones,” Caroline Foster, an astronomer at the University of New South Wales who was not involved in the work, told New Scientist. “The third black hole is better separated, so it is a much cleaner result.”

Could Something Else Be Mimicking Black Holes?

The astronomers spent a substantial portion of the study trying to make the three-black-hole explanation go away rather than leaning into it.

Could the strange signal come from one black hole surrounded by unusually moving gas? Possibly — but that would not easily explain why Webb traced the emission to two different locations.

Could it be a powerful outflow? The team argues that such a flow should leave fingerprints in other elements too, and those were missing.

Supernovae were another possibility. But the central signal remained nearly unchanged across observations taken almost two years apart. A supernova should have faded noticeably over that time. Stellar winds and shock waves also failed to match what Webb saw.

Taken together, the evidence points most strongly to three actively feeding black holes, although the researchers stop short of calling the case definitive.

“This system is in the very, very early universe,” Dougal Dobie, an astronomer at the University of Sydney who was not involved in the research, told New Scientist. “So, how have we ended up in a situation where these three supermassive black holes have formed and come close together in only a billion years or so since the Big Bang?”

One Giant, One Glutton and One Wanderer

The three black holes are far from equal.

The largest is estimated at about 80 million times the Sun’s mass. Its close companion is only about 600,000 solar masses, while the third is around 2 million Suns. Those estimates remain uncertain, but the largest black hole is strikingly massive for a galaxy containing only about 1.3 billion Suns’ worth of stars.

Oddly, the smallest black hole appears to be growing the fastest. It may even be feeding above the so-called Eddington limit, the point where radiation from infalling matter begins pushing strongly against further accretion.

“Observationally, many sources have been found accreting above the Eddington limit,” Übler told IFLScience. “The Eddington limit is a simplified theoretical threshold assuming, for instance, spherical symmetry. Real AGN (active galactic nuclei) are more complex, and thus accretion above the limit is in principle not unexpected.”

The third black hole raises a different question: Is it falling in or being thrown out? It may have arrived inside a smaller galaxy that merged with J0148-4214 and is now sinking toward the center. Alternatively, an earlier black-hole encounter could have kicked it outward.

“Data at higher spatial and spectral resolution would help us to better study the gas kinematics around the black holes, and this could provide some clues,” Übler told IFLScience. “Overall, it seems more plausible to think that the third black hole is sinking towards the centre, perhaps having been brought in through a minor merger.”

The Black Hole Merger Era

Astronomers have found triple black-hole systems before, but not like this one.

A 2019 study of the nearby galaxy SDSS J0849+1114 identified three active, obscured black holes separated by several thousand light-years. This system offered a relatively nearby example of the outcome expected when three galaxies merge.

JWST has since pushed such searches deep into cosmic history. In another 2024 study led by Übler, astronomers found evidence for two black holes separated by about 620 parsecs in a galaxy seen only 740 million years after the Big Bang.

And a GA-NIFS survey of 16 distant active galaxies reported a surprisingly rich population of multiple systems, including a triple AGN and several dual AGNs at separations of 3 to 28 kiloparsecs. Depending on how strictly candidates were counted, roughly 20 to 30 percent of the small sample contained multiple active nuclei — more than some simulations predicted.

J0148-4214 takes that trend to much tighter scales. Its central pair is only 190 parsecs apart.

The researchers estimate that interactions with surrounding stars, gas and dark matter could drag the smaller central black hole inward within roughly 550 million to 660 million years. At first, the objects lose orbital energy through this surrounding material. Later, once they become a tight binary, gravitational waves can take over and eventually drive them together.

The third black hole would take much longer to sink inward under the same simple assumptions — roughly five to six billion years. But three-body interactions are complex and resist neat calculations. Mergers in the real world may happen much faster.

Eventually, descendants of systems like J0148-4214 could become targets for LISA, the planned space-based gravitational-wave observatory. In a deliberately simplified simulation, the researchers estimated a roughly 38 percent chance that a merger resembling the central pair would be detectable by LISA, and an 82 percent chance for a later merger involving the third black hole.

“These results are extremely exciting,” said Roberto Maiolino of the University of Cambridge, a co-author of the study. “They suggest that black hole merging may be an additional, fast route for their rapid growth in the early universe.”

For now, astronomers are seeing J0148-4214 long before any major black hole mergers. We’re now seeing three growing black holes crowded together while the universe itself was still young — a snapshot of the chaotic assembly process that may have built the gargantuan giants found at the centers of galaxies today.

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