A gravitational-wave discovery on Aug. 17 is the first to produce light detected by observatories in space and on the ground. Just 1.7 seconds after the gravitational waves rushed past Earth, NASA’s Fermi Gamma-ray Space Telescope caught high-energy light from an explosion associated with the event. NASA’s Swift, Hubble and Chandra missions, along with dozens of ground-based observatories, later captured the fading glow of the blast’s expanding debris.