Early universe supermassive black holes may be far less massive than thought, study suggests
A reanalysis of James Webb Space Telescope observations using X-ray data proposes that cosmic black holes observed 1 billion years after the Big Bang are 10–30 times smaller than previously estimated.
What happened
Researchers led by Alessandro Trinca of the Italian National Institute for Astrophysics reanalyzed 14 X-ray-silent supermassive black holes detected by JWST in the early universe. They revised mass estimates downward from hundreds of millions of solar masses to 1–10 million solar masses, comparable to or a few times larger than the Milky Way's central black hole. The team interpreted the lack of X-ray emission—despite the black holes' expected rapid feeding on surrounding gas—as evidence that the objects are less massive than previously calculated, not that they emit X-rays weakly. Their model explains the missing X-rays through "super-Eddington" accretion: when black holes feed at extremely high rates, the thick disk of gas surrounding them scatters X-rays, suppressing their apparent brightness.
Context
JWST's discovery of massive black holes in the early universe has posed a puzzle: existing models of black hole growth appeared unable to account for objects reaching hundreds of millions of solar masses before the universe was even 1 billion years old, especially given that these black holes were disproportionately large relative to their small host galaxies. The new analysis resolves both the size anomaly and the host-galaxy mass mismatch. If correct, the lower masses mean black holes would not require continuous growth over hundreds of millions of years, but rather brief episodes of extreme feeding—behavior theoretically consistent with the gas-rich, dynamically active environment of early galaxies. The findings also suggest that rapid super-Eddington accretion, previously considered a constraint on black hole growth, may actually be key to explaining early black hole formation.
What's disputed
The reanalysis is based on a theoretical model of X-ray absorption that has not yet been confirmed observationally. The researchers acknowledge that definitive testing would require detailed study of rapidly accreting black holes at lower redshifts, where environments can be observed in greater detail—observations not yet obtained.