‘We Still Can’t See Dark Matter. But What If We Can Hear It?’

“We may have accidentally detected dark matter back in 2019,” writes ScienceAlert.

“What if instead of trying to see dark matter, scientists attempted to hear it instead?” asks Space.com:
New research suggests dark matter could leave a tiny but discernible imprint in the cacophony of ripples in spacetime called “gravitational waves” that ring through the cosmos when two black holes slam together and merge… Fortunately, when it comes to detecting gravitational waves from colliding black holes, humanity’s instruments, such as LIGO (Laser Interferometer Gravitational-Wave Observatory), are getting more and more sensitive all the time…

Vicente and colleagues searched through data gathered by LIGO and its fellow gravitational wave detectors, KAGRA (Kamioka Gravitational Wave Detector) and Virgo, focusing on 28 of the clearest signals from merging black holes. Of these, 27 appeared to have come from mergers that occurred in the relative vacuum of space. One signal, however, GW190728, first heard on July 19, 2019, and the result of merging binary black holes with a combined mass of 20 times that of the sun and located an estimated 8 billion light-years away, seemed to carry the telltale trace of this merger occurring in a region of dense, “buttery” dark matter.

The team behind this research is quick to point out that this can’t be considered a positive detection of dark matter, but does say it gives us a hint at what to look for and thus where to direct follow-up investigations… “We know that dark matter is around us. It just has to be dense enough for us to see its effects,” said team leader Josu Aurrekoetxea, of the Massachusetts Institute of Technology (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.”
They published their results this week in the journal Physical Review Letters.