Gravitationally lensed starlight (orange) by a supermassive black hole binary. The Einstein ring is shown in blue. Credit: Hanxi Wang Astronomers from the University of Oxford and the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) have outlined a new strategy for uncovering one of the universe's most elusive objects: tightly bound pairs of supermassive black holes. These giant black hole duos are expected to form naturally after galaxies merge. Although astronomers