A new theoretical study suggests a bold approach to find axions, the hypothetical particles that make up dark matter. The team want to use gravitational waves from black holes to finally catch a glimpse of the mysterious substance.
The research, published in Physical Review D, suggests that spinning black holes might be able to generate axions by a process called superradiance. A rotating black hole literally transmits energy to the vacuum that surrounds it, with particles forming from that energy.
“The basic idea is that we’re trying to use black holes... the densest, most compact objects in the universe, to search for new kinds of particles,” Dr. Masha Baryakhtar, from the Perimeter Institute for Theoretical Physics, told Gizmodo.
The researchers claim that a single supermassive black hole could end up producing a staggering 1080 axions, which is more than all the atoms in the universe. These particles, which have just a tiny fraction of the mass of an electron, would end up orbiting the black hole. This seems like a huge number of particles, but their combined mass would be close to 45 times the mass of the Sun. Huge for us, but peanuts when compared to supermassive black holes.
The crucial point of this paper is that this mass would play a role. Maybe not a huge role, but significant enough that our instruments might pick it up. The two LIGO detectors and VIRGO are scanning the sky to detect more gravitational waves. If the axions are there surrounding black holes, the observatories might be soon capable of detecting such a signal.
This shouldn’t be seen as a checkmate in our hunt for dark matter, and it’s probably not even a “check”. However, this paper delivers something very important – it tells physicists what a gravitational signal from these axions will look like. Knowing the exact shape of gravitational waves made it easier for researchers to discover them among the noise, and if black holes are surrounded by massive axion disks, those waves will have a nice and clear signature.