Scientists have identified two supermassive black hole pairs – dubbed “Gondor” and “Rohan” – using a novel detection method that links gravitational wave signals with observations of quasars. This discovery provides the first concrete benchmarks for detecting individual, continuous gravitational waves and mapping merging black holes across the cosmos.
The ‘Beacons’ of Merging Black Holes
The research, conducted by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), leverages the principle that supermassive black hole binaries emit increasing frequencies of gravitational waves as they spiral toward collision. Quasars, powered by actively feeding supermassive black holes, act as “beacons” – radiating detectable gravitational waves when a binary system is present.
This approach is significant because supermassive black hole mergers are five times more likely to occur within quasars. By analyzing 114 Active Galactic Nuclei (AGNs), the bright centers of galaxies, researchers were able to pinpoint Gondor (officially SDSS J0729+4008) and Rohan (SDSS J1536+0411) as prime candidates.
A New Era in Gravitational Wave Detection
NANOGrav’s method combines the detection of background gravitational wave “hum” with precise quasar observations. This dual-pronged approach offers a more efficient way to identify merging black holes than traditional methods.
The team’s findings have immediate implications for gravitational wave astronomy:
- It provides a systematic framework for future detections.
- It facilitates the creation of a gravitational wave background map.
- It could refine our understanding of galaxy mergers, black hole physics, and the nature of gravitational waves themselves.
The naming of the binary systems—after locations in Tolkien’s “The Lord of the Rings”—was partially a tribute to researchers involved (Rohan Shivakumar) and a nod to the dramatic imagery of lit beacons signaling impending conflict in the story. As Mingarelli put it, “The beacons were lit!”
Future Implications
NANOGrav will continue its search for supermassive black hole binaries, aiming to build a comprehensive catalog of mergers. Even a small sample size will contribute significantly to the gravitational wave background map. This research marks a crucial step toward refining our ability to observe and understand some of the universe’s most powerful events.
The ability to systematically detect these systems will unlock new insights into how galaxies evolve and how black holes shape the cosmos.
