Massive black holes form through repeated mergers in dense stellar environments
Updated
Updated · Space.com · May 7
Massive black holes form through repeated mergers in dense stellar environments
15 articles · Updated · Space.com · May 7
Using 153 merger detections from the GWTC4 catalogue, Fabio Antonini's team analysed gravitational-wave data from LIGO, Virgo and KAGRA.
The study, published in Nature Astronomy, found two black hole populations: lower-mass objects from collapsing stars and higher-mass, rapidly spinning ones consistent with hierarchical mergers in globular clusters.
Researchers said the findings support a long-predicted mass gap beginning around 45 solar masses, suggesting black holes above that threshold are more likely built through mergers than direct stellar collapse.
How can colliding black holes reveal more about nuclear physics inside stars than experiments conducted on Earth?
If the most massive stars are obliterated, how does this invisible cosmic process reshape the evolution of galaxies?
Gravitational Waves Reveal Black Holes Growing Through Repeated Mergers in Dense Star Clusters
Overview
In 2024, the LIGO-Virgo-KAGRA collaboration released an expanded catalog of 218 black hole and neutron star mergers, revealing three distinct subpopulations. One group, about 14.5%, features intermediate-mass black holes with chaotic spins, indicating formation in dense globular clusters through hierarchical mergers. These mergers allow black holes to grow beyond the pair-instability mass gap (50-130 solar masses), a natural barrier caused by stellar explosions. Dense star clusters enable repeated mergers by retaining merger remnants despite recoil kicks. While hierarchical black holes show high, misaligned spins and large masses, current observations limit their fraction. Future detectors promise to uncover more about these massive black holes and their dynamic origins.