Using the Subaru Telescope and W. M. Keck and Gemini observatories, astronomers have spotted three dual quasars — merging galaxy systems that have two supermassive black holes on a collision course with each other. SDSS J141637.44+003352.2, a dual quasar at a distance for which the light reaching us was emitted 4.6 billion years ago. The two quasars are 13,000 light-years apart on the sky, placing them near the center of a single massive galaxy...