‘The beacons were lit!’ Scientists name merging supermassive black holes after ‘Lord of the Rings’ locations
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A screenshot of a supermassive black hole collision simulation. | Credit: NASA Goddard Space Flight Center/Scott Noble; simulation data, from Ascoli et al. 2018
When the beacons were lit in “The Lord of the Rings: The Return of the King,” the city of Gondor called to Rohan for help, sounding the death knell for Sauron and his legions. However, when the beacons of the supermassive black hole systems named after these locations in JRR Tolkien’s “Lord of the Rings” novels lit up, it was very good news for scientists.
THE supermassive black hole The Gondor binaries, 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, powered by supermassive black holes.
The logic behind this is that binary supermassive black holes, which spiral to lead to collisions and mergers, emit gravitational waves of increasing frequency as their orbits shrink, creating a hum of gravitational waves in the background. The resulting mergers appear five times more likely to occur in quasars.
The supermassive black holes at the heart of the merging galaxies will move closer and closer until they come together, releasing a titanic wave of energy. | Credit: NASA Goddard Space Flight Center/Scott Noble; simulation data, from Ascoli et al. 2018
This creates quasar beacons that may indicate the unification of supermassive black holes. If any of these beacons emit gravitational waves like the lit beacons of Gondor, this indicates the presence of binary black holes. Thus, this detection technique offers scientists a method to create a cosmic map of these molten titans.
“Our discovery provides the scientific community with the first concrete reference points to develop and test protocols for detecting individual and continuous gravitational wave sources,” Chiara Mingarelli, member of the NANOGrav team. said in a statement.
Mingarelli and his colleagues searched for binary supermassive black holes using their new approach in 114 active galactic nuclei (AGNs), the bright central regions of galaxies where supermassive black holes voraciously feast on surrounding gas and dust.
Mingarelli explained the reason for the unusual name choice for these black hole systems: “The names come from both people and pop culture. Rohan was first, for Rohan Shivakumar, the Yale student who analyzed it first, and Gondor was next, because, well, the beacons were on!
NANOGrav, which first detected a gravitational wave background in 2023, will spend the coming months tracking and identifying supermassive black hole binaries. The team believes that even a relatively small catalog of black hole mergers could help create a background map of gravitational waves. This research could also help scientists better understand galaxy mergers, the physics of black holes and the nature of gravitational waves themselves.
“Our work has established a roadmap for a systemic framework for binary detection of supermassive black holes,” Mingarelli said. “We carried out systematic and targeted research, developed a rigorous protocol and two targets stood out as examples motivating follow-up.”
The team’s results were published on February 5 in Letters from the astrophysical journal.
