For the first time, scientists have directly detected gravitational waves — ripples in space and time — in addition to light from the spectacular collision of two neutron stars. This marks the first time that a cosmic event has been viewed in both gravitational waves and light. The discovery was made using the U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO); the Europe-based Virgo detector; and some 70 ground- and space-based observatories.



The initial detection of the gravitational signal, named GW170817, was first made on Aug. 17 at 8:41 a.m. Eastern Daylight Time; by the two identical LIGO detectors, located in Hanford, Washington, and Livingston, Louisiana. Virgo, situated near Pisa, Italy, also recovered a signal that allowed scientists to precisely triangulate the position of the source in a relatively small patch in the southern sky. At nearly the same time that this detection was made the Gamma-ray Burst Monitor on NASA’s Fermi space telescope had detected a burst of gamma rays. LIGO-Virgo analysis software put the two signals together and saw it was highly unlikely to be a chance coincidence, and another automated LIGO analysis indicated that there was a coincident gravitational wave signal in the other LIGO detector.