Early universe
Webb finds three supermassive black holes sharing one early galaxy
A galaxy seen only 1.3 billion years after the Big Bang contains three black holes—evidence that mergers helped build the giants found in galactic centres today.
Two lie close to the galaxy’s centre and are expected to merge before the more distant third member. The system offers a view of how repeated mergers may have contributed to the rapid growth of massive black holes in the early universe.
The system, reported in Astronomy & Astrophysics as BlackTHUNDER, is seen only about 1.15 billion years after the Big Bang. Researchers identified three actively accreting massive black-hole candidates inside one host system, making it an unusually direct view of several growing black holes during an early stage of galaxy assembly.
Two of the sources sit closer to the centre and are expected to interact and merge before the third. That configuration supports a broader picture in which young galaxies assembled hierarchically: smaller systems came together, bringing their central black holes with them. Repeated mergers and continued feeding could then build the far larger objects observed later in cosmic history.
The evidence depends on interpreting Webb spectroscopy, spatial structure and emission associated with accretion. Calling the objects candidates preserves the distinction between a strong astrophysical interpretation and a directly photographed event horizon. Further observations will test their masses, separations and relationship to the surrounding galaxy.
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