Dark matter hitting black holes could be the source of some fast radio bursts – mysterious blasts of radio waves that come from billions of light years away, first detected 10 years ago.
The stuff we see in space – stars, planets and gas – only makes up about 18 percent of the mass of the universe. The rest is dubbed dark matter, which can’t be seen except through its gravitational interactions with everything else.
Nobody knows exactly what dark matter is, but one hypothesis is that it is formed of still-theoretical particles called axions. These particles, if they exist, would be very light, long-lived, and only interact weakly with other matter around them.
Aiichi Iwazaki at Nishogakusha University in Tokyo says that because the early universe was smaller and offered more chances for axions to attract each other, they would have clumped together to form axion “stars”. Their tendency would be to cluster near the centre of galaxies, making them more likely to pass near the supermassive black holes that sit there and run into the accretion discs of gas that surround them.
“If there are many axion stars in the centres, we expect that some of them collide with the black hole accretion disc,” says Iwazaki. The magnetic field of the disc would cause some axions to decay into individual photons that are then seen on Earth as a fast radio burst (FRB), reaching us at the lower energies of radio wavelengths. There would be enough photons that the signal would still be bright.
Read More: New Scientist