Gravitational wave data from LIGO has uncovered a mass gap in black hole mergers that supports the existence of pair-instability supernovae. These theoretical explosions occur when stars become so massive that their cores spontaneously convert photons into electron-positron pairs, triggering catastrophic oxygen fusion that completely destroys the star without leaving a remnant behind.

Researchers analyzed four years of data from four gravitational wave detectors to identify this gap. They found that the smaller black hole in merger events appears to have a cutoff around 45 solar masses, matching theoretical predictions of roughly 50 solar masses. This suggests stars above this threshold undergo pair-instability supernovae rather than collapsing into black holes.

The team distinguished between first-generation black holes that haven't merged before and second-generation black holes formed from previous mergers. Since most observed mergers involve at least one first-generation black hole, these objects should fall below the pair-instability threshold if the theory is correct. The data supports this, though error bars remain large at about five solar masses.