Title: Multiple Messengers from the Universe: Gravitational Waves and Light from a Neutron Star Merger

Abstract: The detection of gravitational waves and light from the same cosmic source has become one of the most highly-anticipated discoveries in physics and astronomy. Thanks to the recent onset of Advanced LIGO/Virgo, on August 17, 2017, this discovery came to fruition with the first direct detection of a merger of two neutron stars, followed by the detection of electromagnetic emission across ten orders of magnitude in wavelength. The merger, termed GW170817, was localized to a galaxy in our own cosmic neighborhood, allowing us to study the properties of the merger and its environment in unprecedented detail. Here, I describe efforts to localize GW170817 and uncover its properties through gravitational wave and electromagnetic observations. In particular, I present observational evidence for several firsts: the merger of two neutron stars, the launching of a relativistic outflow from the merger, and evidence for the nucleosynthesis of heavy elements in a merger. Finally, I discuss the open questions raised by GW170817 and the bright future ahead for multi-messenger astronomy.