Astronomers detect gravitational waves from colliding galaxies using a galaxy-sized detector

Astronomers have announced their strongest evidence yet for the existence of ultra-low-frequency gravitational waves, which are produced by pairs of supermassive black holes orbiting at the cores of distant galaxies. By observing the regularity of pulsar pulses, radio astronomers from around the world have detected a common rumble in the pulsars, indicating the presence of gravitational waves. The breakthrough has been made possible by improved technology at observatories, and efforts are underway to combine data sets to confirm these signatures. The discovery of ultra-low-frequency gravitational waves has important implications for our understanding of the history of galaxies in the universe.