Binary pairings of small black holes could be used by astronomers in a cosmic game of "hide-and-seek" to hunt much larger, yet more elusive, supermassive black hole binaries. The technique could, therefore, help solve the mystery of how supermassive black holes grew so fast in the early universe.
Detecting black holes is no easy task despite their reputation as fearsome cosmic titans. All black holes are surrounded by a one-way light-trapping boundary called an "event horizon" that ensures they emit no light. Even the supermassive black holes at the hearts of galaxies with masses millions or billions of times that of the sun are only "visible" if they are feasting on a vast amount of surrounding matter or if they are ripping apart an unfortunate star.
