 Six minutes later a single detector at Hanford LIGO, a gravitational-wave observatory, registered a gravitational-wave candidate occurring 2 seconds before the gamma-ray burst.This set of observations is consistent with a binary neutron star merger, as evidenced by a multi-messenger transient event which was signalled by gravitational-wave, and electromagnetic (gamma-ray burst, optical, and infrared)-spectrum sightings.In 2015, the LIGO project was the first to directly observe gravitational waves using laser interferometers.