The history of the black-hole binary system that gave rise to the gravitational waves that were detected for the first time in September 2015 is unravelled in a paper published in Nature this week. This study provides a framework to better understand this and future gravitational wave detections and their sources.
Two merging black holes acted as the source of the gravitational waves (GW150914) that were detected in September 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO) instruments.
Krzysztof Belczynski and colleagues use high-precision numerical models of the formation of binary black holes, arguing that they result from the evolution of binary stars, to predict the properties of gravitational-wave events produced by merging binary black holes. On the basis of these models, the authors calculate that the black holes that gave rise to GW150914 were previously very massive stars (40 to 100 times the mass of the Sun) that collapsed to form binary black holes that subsequently merged. They also estimate that these progenitor stars probably formed about two billion years after the Big Bang. The authors predict that, once instruments at ground-based gravitational-wave observatories acquire optimal sensitivity, about 1,000 black-hole mergers, each with a total mass 20 to 80 times the mass of the Sun, will be detected each year.
“Belczynski and colleagues’ study is tremendously exciting because it examines the effects of a new constraint on how stars and the Universe evolve, identified by GW 150914. With each gravitational-wave signal detected we’ll learn something new”, concludes J.J. Eldridge in a related News & Views article.