Hunt Continues for Gravitational Waves from Black Hole Megamergers

The sound of merging supermassive black holes does not saturate the universe. For the past decade, scientists with the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration have been listening for a constant "hum" of low-frequency gravitational waves. Theoretical work suggests that this hum — generated by collisions involving supermassive black holes, which contain millions or billions of times more mass than the sun — should be detectable at Earth.