The World Today
MADRID, 18 (EUROPA PRESS)
Physicists at the University of Copenhagen have used the magnetic fields of galaxy clusters to observe distant black holes in search of an elusive dark matter particle.
The heaviest structures in the universe, galaxy clusters, are a quadrillion times more massive than the Sun. And axions, mysterious theoretical particles, are vastly lighter than even the lightest atom.
The axion is a hypothetical elementary particle that could hold the key to understanding dark matter, an unknown material believed to account for about 80% of the mass of our universe.
No one has yet proven the existence of axions, something that has eluded researchers for decades. But with an ingenious trick involving distant galaxies, physicists at the University of Copenhagen may have gotten closer than ever, they say.
Instead of using a ground-based particle accelerator, like the one at CERN, the researchers turned to the cosmos and used it as a kind of giant particle accelerator. Specifically, they looked for the electromagnetic radiation emitted by the nuclei of distant, very bright galaxies, each with a supermassive black hole at its center.
They then observed this radiation as it passed through the vast magnetic fields of galaxy clusters, where some of it could, hypothetically, transform into axions. This transformation would leave behind tiny, random fluctuations in the data. However, each signal is so weak that, on its own, it is lost in the background noise of the universe.
So the researchers introduced a novel concept. Instead, they observed a total of 32 supermassive black holes located behind galaxy clusters and combined the data from their observations.
A PATTERN SIMILAR TO THE AXION SIGNATURE
Examining the data, the researchers were surprised to discover a pattern that resembled the signature of the elusive axion particle.
“Normally, the signal from these particles is unpredictable and appears as random noise. But we realized that by combining data from various sources, we had transformed all that noise into a clear, recognizable pattern,” explains Oleg Ruchayskiy, associate professor at the Niels Bohr Institute at the University of Copenhagen and lead author of a paper in Nature Astronomy titled “Constraints on axion-like particles from active galactic nuclei seen across galaxy clusters,” which seeks to study the axion.
"It presents itself as 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's still very tantalizing and exciting. We could call it a cosmic whisper, now loud enough to hear."
CLOSER TO THE DISCOVERY OF DARK MATTER
While the pattern revealed by the scientists does not constitute definitive proof of the existence of axions, the research by Ruchayskiy and his colleagues brings us closer to understanding what dark matter is.
"This method has significantly expanded our knowledge of axions. It has allowed us, in essence, to map a large area that we know doesn't contain axions, narrowing the space where they can be found," says postdoctoral researcher Lidiia Zadorozhna, a Marie Curie Fellow at the Niels Bohr Institute and one of the lead authors of the new paper.
