Collision and merger of two black holes, resulting in the first detection of gravitational waves, GW150914, by LIGO. By The SXS (Simulating eXtreme Spacetimes) Project , [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

https://commons.wikimedia.org/wiki/File:Black_hole_collision_and_merger_releasing_gravitational_waves.jpg