The massive black hole has been dubbed GW231123. Its unusual size and behavior is challenging scientists' understanding of black hole formation, Hannam said. Previously, the largest known black hole that came from a merger was about 140 times the mass of the sun.

To date, the collaboration has detected dozens of merger events since its first Nobel Prize-winning discovery. Early detected mergers involved either two black holes or two neutron stars. In 2021, LIGO/Virgo/KAGRA confirmed the detection of two separate "mixed" mergers between black holes and neutron stars.