Webb Telescope Spots Triple Black Holes in Early Universe

The James Webb Space Telescope has captured a galaxy containing three supermassive black holes, including two on the cusp of merging, in a discovery that provides unprecedented insight into how these cosmic giants grew in the early universe. The findings, published in the journal Astronomy & Astrophysics, mark the first time a triplet of active black holes has been observed in a single galaxy at such a great distance.

An international team led by the Max Planck Institute for Extraterrestrial Physics identified three actively accreting supermassive black holes in the galaxy J0148-4214, located more than 12.5 billion light-years from Earth. The galaxy’s light has traveled for 12.5 billion years, showing it as it appeared only about 1.2 billion years after the Big Bang.

A Cosmic Surprise

Hannah Übler, research group leader at MPE and lead author of the study, and her colleagues had set out two years ago to map parts of the ancient cosmos using JWST images, hoping to find galaxies containing two black holes. Instead, they found a galaxy with three.

“This is the first evidence of three active black holes in a single galaxy in the distant Universe,” Übler said.

Two of the black holes are located in the galactic center, separated by only 620 light-years in projection, while a third sits in the outer region of the galaxy, approximately 5,500 light-years from the center. The analysis yields black hole masses of approximately 80 million, 0.6 million, and 2 million solar masses respectively.

How the Discovery Was Made

The discovery was made possible by JWST’s NIRSpec-IFU (Near-Infrared Spectrograph - Integral Field Unit) spectroscopy, which allows spatially resolved analysis of the galaxy’s emission. The researchers identified the black holes through their spectral fingerprints: signatures of hydrogen atoms moving at high velocity in the gravitational potential of the black holes.

Steven Finkelstein, an astronomer at the University of Texas at Austin who was not involved in the research, called it “a really cool mode” of Webb’s powerful near-infrared spectrograph, which can tease apart the individual wavelengths of light hitting the instrument. He noted that “the only thing in the universe we know of” that can make gases behave that way is the pull of a supermassive black hole that is still growing.

At Hubble’s resolution, the galaxy would appear as just a few pixels in an image—too small to make out the contours of its three resident black holes, as New Scientist reported.

Black Hole Growth in the Early Universe

The discovery addresses one of the most fundamental questions in astrophysics: how do supermassive black holes get so big? As Finkelstein put it, “How black holes get so big is one of the outstanding questions in astrophysics.”

Scientists understand how smaller black holes form—when a star dies, it can explode and collapse to create a black hole several times the mass of the sun. But supermassive black holes, equivalent to millions or billions of solar masses, present a major puzzle.

The new findings suggest that mergers and interactions in the early universe may have contributed to the rapid growth of supermassive black holes. “The assumption has always been that these black holes started to grow in the early universe,” Übler said. “Now we are seeing them in action.”

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

The Impending Merger

The two central black holes are expected to merge within the next few hundred million years, with a dynamical friction time estimate of approximately 700 million years. This merger could be detectable by future gravitational wave observatories like LISA (Laser Interferometer Space Antenna).

“It suggests that processes in the early Universe were efficient at bringing massive black holes together, setting the stage for the massive black hole mergers we expect to detect with future gravitational wave observatories,” Übler said.

Dr. Giovanni Mazzolari, second author of the study and researcher at MPE, noted: “The JWST data allowed us not only to identify the three black holes, but also to estimate their masses, accretion rates, and the stellar mass of the galaxy. We find a total stellar mass of about 1.3 billion suns, and the black holes represent a significant fraction of that.”

The Mystery of the Third Black Hole

The third black hole, located off-nucleus, presents an intriguing puzzle. It may be the remnant of a previous merger, displaced from the center by a gravitational recoil kick, or it may currently be migrating inward.

Caroline Foster, an associate professor at the University of New South Wales who was not involved in the discovery, told New Scientist that “the fingerprints look like black holes and the ‘shape’ is best explained with two separate ones. The third black hole is better separated, so it is a much cleaner result. Maybe it is falling into the galaxy for the first time, or maybe it has been ejected by interactions with the other two.”

Julie Comerford, an astrophysics professor at the University of Colorado Boulder who was not part of the study, said it’s possible the third black hole “may join the merger in the future, or maybe it was ejected as a result of an even earlier merger.”

Dougal Dobie of the University of Sydney, who also wasn’t involved in the discovery, expressed astonishment at the find: “This system is in the very, very early universe. 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?”

Implications for Astrophysics

The observations, detailed in the paper “BlackTHUNDER: Evidence of three massive black holes in a z ∼ 5 galaxy” published in Astronomy & Astrophysics, demonstrate that integral field spectroscopy is an important tool for identifying multiple active black holes in distant galaxies. Without the spatially resolved information provided by NIRSpec-IFS, only one of the three black holes would likely have been detected.

The discovery adds to a growing body of evidence from JWST that multiple massive black hole systems were likely common in the early universe. Previous triple black hole systems had been observed only in the nearby universe, making this the first time a triplet has been observed so far from Earth.

What’s Next

As more telescopes come online and technology advances, astronomers expect to find more such galaxies. The discovery raises several outstanding questions: How common are triple black hole systems in the early universe? Will the two central black holes actually merge, and what will be the gravitational wave signature? And what is the fate of the third off-nuclear black hole?

For now, the finding offers a remarkable window into the dynamics of black hole collisions and galaxy evolution—and a glimpse of what future gravitational wave observatories may detect.