The challenge and promise of LIGO’s heavy black holes

Maximiliano Isi (Columbia University)

May 04, 2026

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Abstract: The LIGO-Virgo instruments have so far detected ~300 mergers of compact objects, most of them black holes. These detections give us an increasingly detailed view of the distribution of black hole masses and spins, with implications for stellar physics and the dynamics of dense astrophysical environments. While many interesting features have emerged, one of the most puzzling is the existence of merging black holes exceeding 60 solar masses, several of which also appear to spin extremely fast. Such systems are difficult to explain with our current theories of stellar binary evolution and lack a clear formation pathway. They also present a big challenge to our modeling and analysis techniques, since their signals are short and dominated by the least-understood portion of the merger process in general relativity. In this talk, I will outline the challenge and promise of understanding LIGO’s heavy black holes from the point of astrophysics, general relativity and data analysis, which, as LIGO continues to observe, may well be the key to some of the most pressing questions in the field.