In this video, ESA scientists Paul McNamara and Matteo Guainazzi explain how the observing power of LISA and Athena could be combined to study the merging of two supermassive black holes and their mysterious aftermath for the first time.

LISA, the Laser Interferometer Space Antenna, will be the first space-borne observatory of gravitational waves – fluctuations in the fabric of spacetime produced by the acceleration of cosmic objects with very strong gravity fields, like pairs of merging black holes. Athena, the Advanced Telescope for High-ENergy Astrophysics, will be the largest X-ray observatory ever built, investigating some of the hottest and most energetic phenomena in the cosmos with unprecedented accuracy and depth. Currently, under study, both missions are scheduled for launch in the early 2030s.

Credits: Event Horizon Telescope Collaboration (black hole image); NASA, ESA and F. Summers, STScI (Hubble Ultra Deep Field flythrough and galaxy merger); Simulating eXtreme Spacetimes Project (gravitational waves and merging black holes); AEI/Milde Science Communication/exozet (LISA orbit sequence); ESA/Hubble, NASA, M. Kornmesser (active galactic nucleus)