GW170817

GW170817 is a gravitational-wave signal detected by LIGO and Virgo on 17 August 2017 from the merger of two neutron stars in the galaxy NGC 4993, about 140 million light-years away. It was the first gravitational-wave detection matched to an electromagnetic event.

A short gamma-ray burst, GRB 170817A, arrived 1.7 seconds later, and some 70 observatories followed the aftermath across the spectrum, a breakthrough for multi-messenger astronomy. Science named the discovery its 2017 Breakthrough of the Year.