#GWGreatestHits Less than two years after the first direct detection of gravitational waves, a pair of colliding neutron stars were identified as the source of a gravitational wave signal. This event, called GW170817, was one with two breakthroughs! The detection by the LIGO-Virgo collaboration was confirmed by a large number of telescopes that studied the wide variety of electromagnetic signals that accompanied the merger, marking the beginning of multi-messenger astronomy.