Astrophysics: Recipe for a black-hole merger

Krzysztof Belczynski et al. present numerical simulations of the formation of binary black holes that provide a framework for interpreting the recent detection of the first gravitational-wave source (known as GW150914) a merger of two massive black holes. Their models imply that these events take place in an environment where the metallicity is less than 10 per cent of that of the Sun, and that the progenitors are stars with initial masses of 40100 solar masses that interact through mass transfer and a common-envelope phase. The calculations predict detections of about a thousand black-hole mergers per year once gravitational-wave observatories reach full sensitivity.