Universe-scale particle accelerator finds hints of elusive axions
Axions are the light particles that scientists suspect make up dark matter. The jets from distant black holes have revealed tantalising hints of the elusive particles that have not been detected yet.
Dark matter is a mysterious substance that makes up 85 per cent of the matter in the universe. Scientists have not directly observed dark matter yet, but they are sure that it exists. The axion is a hypothetical elementary particle, that is believed to make up dark matter. While we do not know what dark matter is yet, there are signs to indicate that the dark matter particles are slow-moving or cold. Axions are also believed to be much lighter than the lightest atom. Now, scientists have used the most massive structures in the universe, galaxy clusters to come closer than ever before to detecting the elusive axions.
The scientists used the entire universe as a giant particle accelerator, investigating electromagnetic radiation emitted by the cores of distant, and bright galaxies, that host actively feeding supermassive black holes. In theory, the radiation from the supermassive black holes passing through the vast magnetic fields of galaxy clusters could transform some of the radiation into axions. However, the individual signals were faint and got lost in the background noise, so the researchers combined observations from 32 supermassive black holes positioned behind galaxy clusters. The researchers were able to isolate a pattern that resembled the signature of axions.
The signature of axions
A paper describing the findings has been published in Nature Astronomy. Senior author of the paper, Oleg Ruchayskiy explains, "Normally, the signal from such particles is unpredictable and appears as random noise. But we realized that by combining data from many different sources, we had transformed all that noise into a clear, recognizable pattern. It shows up like a unique step-like pattern that shows what this conversion could look like. We only see it as a hint of a signal in our data, but it is still very tantalizing and exciting. You could call it a cosmic whisper, now loud enough to hear."