GW150914

GW150914 is the designation given to the first direct detection of gravitational waves, observed on September 14, 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors in Livingston, Louisiana, and Hanford, Washington. The signal originated from the merger of two black holes and marked the beginning of gravitational-wave astronomy.

The source black holes had masses of about 36 and 29 solar masses, forming a final black hole of about 62 solar masses; the remaining roughly 3 solar masses were radiated away as energy in gravitational waves. The waveform exhibited the characteristic inspiral, merger, and ringdown predicted by general relativity, with the signal lasting about a fraction of a second and sweeping upward in frequency.

The event occurred roughly 1.3 billion light-years from Earth, at a distance of about 410 megaparsecs. The signal was detected in both LIGO detectors with a few-millisecond time difference, consistent with a gravitational wave propagating at the speed of light. Initial localization spanned thousands of square degrees, and subsequent analyses refined sky position with the help of additional detectors in the network.

An international follow-up campaign searched for electromagnetic counterparts but found no confirmed counterpart to this binary black hole merger. The discovery was published in 2016 and significantly impacted physics and astronomy by confirming a major prediction of general relativity and inaugurating gravitational-wave astronomy. In 2017, the Nobel Prize in Physics was awarded to Weiss, Barish, and Thorne for their roles in LIGO and the observation of gravitational waves.