JWST Discovers the Closest-Known Pair of Feeding Supermassive Black Holes in the Early Universe — And a Trio in Another Galaxy

Why earlier telescopes missed it: LID-1166 was first flagged as an X-ray source in the Chandra COSMOS Legacy Survey, but it remained completely undetected in even the deepest Hubble Space Telescope images . The black holes are buried in dense gas and dust that block visible and near-infrared light .

JWST's instrument of choice: The team, led by Hyewon Suh of NSF NOIRLab, used JWST's Near-Infrared Spectrograph (NIRSpec) . NIRSpec revealed two compact, glowing sources separated by 4,900 light-years, each showing spectral signatures of gas swirling at high speeds — unmistakable signs of actively feeding supermassive black holes (active galactic nuclei, or AGN) . Co-author Roberto Decarli said: 'This step of the discovery could happen only thanks to the exquisite imaging and spectroscopic capabilities of the JWST, and in particular its instrument NIRSpec. Similar observations from the ground would be extremely challenging due to the poor transparency of the atmosphere at these wavelengths.'

What ALMA added: The Atacama Large Millimeter/submillimeter Array (ALMA) detected large pools of cold gas associated with each AGN . Decarli noted this 'points to the two AGN residing in the center of two galaxies on the verge of merging.' The presence of a cold gaseous galactic environment around each black hole helped rule out exotic alternative formation scenarios and confirmed a genuine gas-rich galactic merger . The study has been accepted for publication in Nature Astronomy (preprint arXiv:2607.19491) .

A Separate First: Three Active Black Holes in One Galaxy

A simultaneous study, led by Hannah Übler at the Max Planck Institute for Extraterrestrial Physics, identified three actively accreting supermassive black holes within the single galaxy J0148-4214 . The galaxy is more than 12.5 billion light-years from Earth (redshift z=5.0167), corresponding to roughly 1.2 billion years after the Big Bang .

Configuration of the trio: Two of the black holes are located close together in the galactic center, separated by only 620 light-years in projection, suggesting they are on the verge of merging. A third black hole sits farther out in the galaxy's outer region, about 5,500 light-years from the center . The masses range from a few million to about 80 million solar masses .

Detection method: The team used JWST's NIRSpec in Integral Field Unit mode (NIRSpec-IFS) — spatially resolved spectroscopy — to detect the black holes through their spectral fingerprints. Each was identified by broad H-alpha emission (FWHM 430–2,920 km/s) without a forbidden-line counterpart, a clear signature of gas orbiting a massive black hole .

This is the first evidence of three active supermassive black holes in a single galaxy in the distant universe . Übler said: '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.' The study was published in Astronomy & Astrophysics as part of the BlackTHUNDER project .

What These Discoveries Mean

Together, the two results provide a new window into a critical phase of cosmic history. They show that supermassive black holes were not only present but were actively merging and growing in gas-rich environments less than 1.5 billion years after the Big Bang. JWST's ability to see through dust — using infrared light that shorter wavelengths cannot penetrate — has been the key to unveiling these hidden black hole systems. As the LID-1166 study notes, earlier telescopes like Hubble were blind to these objects, which are shrouded in the very gas and dust that feeds them .