When the beacons were lit in “The Lord of the Rings: The Return of the King,” the city of Gondor called to Rohan for aid, spelling doom for Sauron and his legions. However, when the beacons of supermassive black hole systems named for these locations in J.R.R. Tolkien’s “Lord of the Rings” novels were lit up, it was exceptionally good news for scientists.

The supermassive black hole binaries Gondor, officially designated SDSS J0729+4008, and Rohan, SDSS J1536+0411, were discovered by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) using a new technique that uses the background hum of ripples in space called “gravitational waves” in conjunction with observations of quasars, which are powered by feeding supermassive black holes.

The logic behind this is that supermassive black hole binaries, which spiral together to lead to collisions and mergers, emit gravitational waves of increasing frequency as their orbits shrink, creating a background hum of gravitational waves. The resultant mergers seem to be five times more likely to be found in quasars.

That makes quasars beacons that can indicate the unification of supermassive black holes. If one of these beacons radiates gravitational waves like the lit beacons of Gondor, it indicates binary black holes are present. Thus, this detection technique offers scientists a method to create a cosmic map of these merging titans.