Astrophysics: Confirming a forbidden range of black-hole masses (Nature)
2 April 2026
Evidence for a forbidden range of black-hole masses is detected in data from the fourth Gravitational-Wave Transient Catalog (GWTC-4) from LIGO–Virgo–KAGRA — a global network of gravitational-wave observatories — looking at binary black-hole systems. The findings, reported in Nature, support theories that black holes of certain masses cannot exist due to instabilities, but only in the secondary-mass black holes (the smaller of two black holes in certain binary systems). The discovery may offer insights into the evolution of stars and black holes.
Stellar evolution theory predicts that certain very massive stars undergo explosive events known as pair instability supernovae, which can be so powerful and disruptive that it leaves no black hole remnant. This process is expected to result in a gap in the range of masses that can exist: the pair-instability gap, which is predicted to range from 50 to 130 times the mass of the Sun. Evidence for such a gap has been lacking, but gravitational-wave observatories are a promising way to probe the outcomes of pair instability supernovae as they can detect signals from such massive cosmic events.
Data from the fourth catalogue of gravitational waves detected by the LIGO–Virgo–KAGRA collaboration (with observatories in the USA, Italy and Japan) focus on the distribution of masses within binary black-hole systems. The analyses provide evidence for the pair-instability gap in secondary-mass black holes in these systems, Hui Tong and colleagues report. The gap is not observed in the larger of the two black holes in the binary, but there is an absence of secondary black holes between roughly 44 and 116 solar masses. This gap lines up with a mass range in which binary black-hole spins seem to change in behaviour, which could reflect an underlying pair-instability process, the authors suggest.
The authors propose that the primary black hole in such systems could exist within the forbidden mass gap as they may have formed in a different way to secondary black holes from pair instability supernovae. The findings could improve understanding of how massive stars evolve.
- Article
- Published: 01 April 2026
Tong, H., Fishbach, M., Thrane, E. et al. Evidence of the pair-instability gap from black-hole masses. Nature (2026). https://doi.org/10.1038/s41586-026-10359-0
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