Monash researchers find secondary black hole mass gap in binary systems
Updated
Updated · physicsworld.com · May 1
Monash researchers find secondary black hole mass gap in binary systems
5 articles · Updated · physicsworld.com · May 1
Using LIGO-Virgo-KAGRA's GWTC-4 catalogue, Hui Tong's team found no secondary black holes between 44 and 116 solar masses.
The primary black holes showed no comparable gap, but the researchers said a similar mass range marks where primaries begin spinning faster, hinting some formed through earlier black hole mergers.
Published in Nature, the study bolsters the long-predicted pair-instability supernova theory and suggests future gravitational-wave observatories could test it with far larger samples.
If the universe has a 'forbidden zone' for making black holes, how are even larger ones being discovered within it?
Could gravitational echoes from dead stars reveal new particles that Earth-based experiments cannot find?
Unveiling the Secondary Black Hole Mass Gap: Gravitational-Wave Evidence and the Role of Pair-Instability Supernovae
Overview
In 2025, gravitational-wave observations confirmed a secondary black hole mass gap between 44 and 116 solar masses, caused by pair-instability supernovae that prevent single stars from forming black holes in this range. Stars with helium cores between 40 and 62 solar masses undergo pulsational pair-instability supernovae, limiting black hole masses to about 50 solar masses, while more massive cores explode completely, leaving no remnant. However, primary black holes within the gap exist due to hierarchical mergers of smaller black holes in dense clusters, which also produce distinctive high and randomly oriented spins. This mass gap helps refine stellar models and nuclear reaction rates, and intermediate-mass black holes near the gap serve as powerful tools for precise cosmological measurements.