Scientists have developed a new technique that could turn black hole collisions into cosmic detectors for dark matter, revealing faint traces hidden inside gravitational waves.
Dark matter is believed to account for most of the matter in the universe, yet it appears to interact with ordinary matter only through gravity. Scientists think that if two black holes collide while moving through a dense region filled with dark matter, the resulting gravitational waves could contain subtle traces of that invisible material.
Researchers now believe those traces may be detectable in gravitational waves measured on Earth.
A team from MIT and several European institutions developed a method to predict how gravitational waves would differ if merging black holes traveled through dark matter instead of empty space. They tested the approach using publicly available data collected by LIGO-Virgo-KAGRA (LVK), the international network of observatories that detects gravitational waves from black hole mergers and other distant cosmic events.
The researchers analyzed signals recorded during LVK’s first three observing runs. Among the 28 clearest events, 27 matched expectations for black holes merging in a vacuum. One signal, known as GW190728, appeared to show possible evidence of a dark matter effect.
The team stresses that this is not a detection of dark matter. Instead, the method offers a new way to search gravitational-wave data for potential signs that can later be tested with additional studies.
“We know that dark matter is around us. It just has to be dense enough for us to see its effects,” says Josu Aurrekoetxea, a postdoc in the MIT Department of Physics. “Black holes provide a mechanism to enhance this density, which we can now search for by analyzing the gravitational waves emitted when they merge.”
Aurrekoetxea and his colleagues published their findings in Physical Review Letters. The study also included LVK member Soumen Roy of Université Catholique de Louvain (UCLouvain) in Belgium, Rodrigo Vicente of the University of Amsterdam, Katy Clough of Queen Mary University of London, and Pedro Ferreira of Oxford University.
Why Dark Matter Remains So Elusive
Dark matter remains one of the biggest mysteries in physics. Unlike ordinary matter, it does not interact with light or other forms of electromagnetic energy, making it effectively invisible. Scientists can infer its existence only through gravity.
Astronomers first suspected dark matter while studying how gravity bends light around galaxies, an effect called gravitational lensing. The visible matter in galaxies alone cannot explain these distortions, leading researchers to conclude that an unseen form of matter must also be present. Current estimates suggest dark matter could make up more than 85 percent of all matter in the universe.
One leading theory proposes that dark matter may consist of extremely light particles called “light scalar” particles. Near black holes, these particles may behave not only like matter but also like waves.
Scientists predict that when these waves encounter a rapidly spinning black hole, the black hole can transfer some of its rotational energy to the dark matter. This process, known as superradiance, could dramatically increase the density of dark matter surrounding the black hole.
At sufficiently high densities, that dark matter could leave detectable signatures in the gravitational waves produced when black holes merge.
Simulating Gravitational Waves in Dark Matter
But exactly what would that imprint look like? And could such an imprint be detectable in gravitational waves that arrive on Earth, from black holes that merged many millions of light years away?
For answers to those questions, Aurrekoetxea and his colleagues developed a model to predict the gravitational waveform, or the pattern of gravitational waves that two black holes would produce, if they collided in an environment of dark matter, versus in a vacuum (empty space, with no dark matter).
For their new study, the team performed detailed numerical simulations to predict the gravitational wave that would be produced given various properties of two colliding black holes — a system known as a “black hole binary.” They considered black hole binaries across a range of scenarios and properties, for example, varying the size and mass of each black hole, the environment of dark matter that the black holes might pass through, and the density of the dark matter that the black holes would spin up.
They designed the model to predict what a gravitational wave from a black hole binary would look like if it carried an imprint of dark matter, and furthermore, what that wave would look like if it traveled a given distance across space and time, to eventually arrive at a detector on Earth.
With their model, they looked to see whether any gravitational-wave signals that have been detected on Earth match their predicted patterns of dark matter imprints. To do so, they applied the model to publicly-available data recorded by LVK over the observatories’ first three observing runs. The observatories have picked up hundreds of gravitational-wave signals during this period. For their purposes, the researchers focused on the clearest signals, comprising gravitational waves from 28 separate events.
For each event, the team compared the pattern of the actual gravitational wave against their model of what the signal would look like if it were generated by the same event in an environment of dark matter. They also compared the gravitational wave to the more expected scenario in which the signal was produced in a vacuum.
One Signal Stands Out
Of the 28 clearest signals that they analyzed, 27 were solidly within the predictions for having been produced in a vacuum. However, the pattern of one event, GW190728, showed a “preference,” or an agreement with the team’s dark matter model. In other words, the signal may carry an imprint of dark matter.
GW190728 is a gravitational wave that is named after the date that it was detected — on July 28, 2019. Scientists previously determined that the gravitational wave originated from a black hole binary with a total mass of about 20 times the mass of the sun. With their model, the team showed that such a system could have merged through a dense cloud of dark matter and produced a similar gravitational wave to GW190728.
“The statistical significance of this is not high enough to claim a detection of dark matter, and further checks should be performed by independent groups,” Aurrekoetxea says. “What we think is important to highlight is that without waveform models like ours, we could be detecting black hole mergers in dark matter environments, but systematically classifying them as having occurred in vacuum.”
“We now have the potential to discover dark matter around black holes as the LVK detectors keep collecting data in the coming years,” says co-author Soumen Roy, who led the data analysis part of the work. “It is an exciting time to search for new physics using gravitational waves.”
“Using black holes to look for dark matter would be fantastic,” adds co-author Rodrigo Vicente, who developed the analytical model of the signal. “We would be able to probe dark matter at scales much smaller than ever before.”
Reference: “Scalar Fields around Black Hole Binaries in LIGO-Virgo-KAGRA” by Soumen Roy, Rodrigo Vicente, Josu C. Aurrekoetxea, Katy Clough and Pedro G. Ferreira, 12 May 2026, Physical Review Letters.
DOI: 10.1103/fv9z-zkxx
This work was supported, in part, by the U.S. National Science Foundation and MIT’s Center for Theoretical Physics – a Leinweber Institute.
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