Neutron Star Merger Seen and Heard For

O ver thousands of years, astronomy has evolved from hand-drawn maps of the night sky to breathtaking telescope images of the far-away cosmos. Yet despite this advance in technology, most of our information about the Universe has come from photon messengers. This changed in September 2015 with the detection of gravitational waves from a black hole merger at the Laser Interferometer Gravitational-Wave Observatory (LIGO) [1], an achievement that was recognized with this year’s Nobel Prize in Physics. The chirp-like signal, caused by a traveling ripple through spacetime, gave us a new way to sense the Universe, like being able to hear, when before we could only see. Now LIGO and its sister experiment, Virgo, have broken ground yet again with their joint detection of gravitational waves from the merger of two neutron stars [2] (see Video 1). Unlike a black hole merger, which is practically invisible, a neutron star merger event (Fig. 1) is accompanied by emission across the electromagnetic spectrum. Data from multiple telescopes show that the detected merger produced another cosmological spectacle, a short gamma-ray burst [3]. This long-awaited ability to simultaneously compare the sights and “sounds” from the same object in space opens up entirely new ways to explore the relationship between gravity, light, and matter.