Researchers from MIT and European institutions have developed a new technique to detect potential signs of dark matter in gravitational waves produced by merging black holes. Applying this method to data from the LIGO-Virgo-KAGRA (LVK) observatory network, they found one gravitational-wave event, GW190728, whose pattern may contain an imprint of dark matter.
Dark matter, which makes up an estimated 85 percent of the universe’s matter, remains undetectable except through its gravitational effects. It does not interact with light or other electromagnetic forces, making direct observation impossible. One hypothesis suggests that clouds of light scalar dark matter particles could amplify around spinning black holes through a process called superradiance, increasing dark matter density and potentially altering gravitational-wave signals emitted during black hole mergers.
Modeling Dark Matter’s Impact on Gravitational Waves
The team developed detailed numerical simulations to predict how gravitational waves would appear if their source black holes merged within dense regions of dark matter rather than in empty space. Their model accounted for variables such as black hole mass and spin and the properties of the surrounding dark matter environment. Using this model, the researchers analyzed the 28 clearest gravitational-wave signals detected during LVK’s first three observational runs.
In comparing actual signals to their model predictions, the researchers found that 27 events matched patterns expected from mergers occurring in vacuum environments. However, the signal GW190728, detected on July 28, 2019, showed a preference for the dark matter-environment model. This binary black hole merger involved black holes with a combined mass about 20 times that of the sun.
Implications and Next Steps
The authors caution that the statistical significance of the potential dark matter signature in GW190728 is not sufficient to claim a definitive detection. They stress the importance of waveform models like theirs to avoid misclassifying black hole mergers that occur within dark matter as vacuum events. Continued data collection by LVK and future independent analyses will be essential for confirming any dark matter imprints.
According to MIT postdoctoral researcher Josu Aurrekoetxea, “Black holes provide a mechanism to enhance dark matter density, which we can now search for by analyzing gravitational waves.” Soumen Roy of Université Catholique de Louvain adds, “We now have the potential to discover dark matter around black holes as the LVK detectors keep collecting data in the coming years.”
Background
The search for dark matter signatures in gravitational waves offers a novel probe of dark matter properties at scales smaller than previously accessible. While dark matter is inferred from gravitational lensing effects on galactic scales, its fundamental nature remains uncertain. The light scalar dark matter model predicts wave-like behavior around black holes, leading to amplifications detectable in gravitational-wave data.
This research, published in Physical Review Letters, involved collaborators from MIT, Université Catholique de Louvain, University of Amsterdam, Queen Mary University of London, and Oxford University. Funding came from the U.S. National Science Foundation and MIT’s Center for Theoretical Physics.
Sources
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