Observing gravitational waves from merging black holes may reveal new insights into dark matter, a study led by University College London suggests.
The research, published in the journal Physical Review D, used computer simulations to study the production of gravitational wave signals in simulated universes with different types of dark matter. Their findings show that counting the number of black hole merger events detected by the next generation of observatories could tell us whether or not dark matter is interacting with other particles, and thus help pinpoint what it’s made of. Cosmologists generally consider dark matter to be one of the biggest missing pieces in our understanding of the cosmos. Despite strong evidence that dark matter makes up 85% of all matter in the universe, there is currently no consensus on its underlying nature. This includes questions such as whether dark matter particles can collide with other particles, such as atoms or neutrinos, or pass directly through them unaffected.
One way to test this is to look at how galaxies form in dense clouds of dark matter called halos. If dark matter collides with neutrinos, the dark matter structure is scattered, resulting in fewer galaxies forming. The problem with this method is that the disappearing galaxies are very small and very distant from us, so it is difficult to see whether they are there or not, even with the best available telescopes. Instead of targeting missing galaxies directly, the authors of this study propose using gravitational waves as an indirect measure of their abundance. Their simulations show that in models where dark matter collides with other particles, there are significantly fewer black hole mergers in the distant Universe.
While this effect is too small to be seen by current gravitational wave experiments, it will be a primary goal for the next generation of observatories currently being planned. The authors hope that their methods will help stimulate new ideas for using gravitational wave data to explore the large-scale structure of the universe and shed new light on the mysterious nature of dark matter. Dr. Alex Jenkins, one of the study’s lead authors, said in a statement: “Gravitational waves are a powerful new tool for observing the distant Universe. The next generation of observatories will detect hundreds of thousands of black hole mergers every year, giving us unprecedented information about the structure and evolution of the cosmos.”
Co-author Dr Sownak Bose from Durham University said: “Dark matter remains one of the enduring mysteries in our understanding of the universe. This means that it is especially important to continue to identify new ways to explore dark matter models, combining both existing and current models”. new probes to test the model predictions to the fullest.