An international collaboration of astrophysicists that includes researchers from Yale has created and tested a detection system that uses gravitational waves to map out the locations of merging black holes—known as supermassive black hole binaries—around the universe. Such a map would provide a vital new way to explore and understand astronomy and physics, just as X-rays and radio waves did in earlier eras, the researchers say. The new protocol demonstrated by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) offers a detection protocol to populate the map.