The merger wasn’t just the biggest ever, but also an event so rare that it challenges existing models for black hole genesis.

What occurs when the universe plays a cosmic curveball, breaking down long-standing assumptions about how black holes form? On 23 November 2023, the LIGO-Virgo-KAGRA Collaboration observed a gravitational wave signal GW231123 that would become an instant classic in the field of astrophysics.

A collision observed between two black holes, each more massive than a hundred suns, is the largest merger of its kind ever recorded, according to new research.