In September 2015, gravitational waves (GWs) were detected for the first time by the LIGO detectors, the two laser interferometers in the United States. It was found that detected GWs originate from the coalescence of two black holes (BHs) in a binary, each weighing about 30 times the mass of the Sun (30 solar mass). Although there have been indirect observations of BHs in the X-ray binaries, their masses are at most 15 solar masses.
With the announcement, on 11 February 2016, of the first detection ever of a gravitational wave by the LIGO and Virgo Collaborations, a New Astronomy, based on listening to the space-time vibrations, was born.
This long-awaited wave, 100 years after the theoretical prediction by Albert Einstein and 50 years after the first experimental efforts, arrived on Earth on 14 September 2015 and was finally perceived by humans with very smart “microphones”.