Scientists may be a step closer to solving a cosmic mystery that has puzzled researchers for decades: where do the universe’s most powerful particles—ultra-high-energy cosmic rays—come from?
A new study from researchers at the Norwegian University of Science and Technology (NTNU) suggests the answer might lie in the massive winds blowing out from supermassive black holes.
Cosmic rays aren’t actually rays, but tiny, high-speed particles—mainly atomic nuclei—that zoom through space at nearly the speed of light.
Scientists have long known about these particles, and they typically come from energetic cosmic events like exploding stars or spinning neutron stars.
But every so often, cosmic rays are discovered with much more energy than expected—so powerful that their origin remains a mystery even 60 years after the first one was spotted.
Now, a team led by Ph.D. student Domenik Ehlert and associate professor Foteini Oikonomou at NTNU has a new idea.
Their research, recently published in the Monthly Notices of the Royal Astronomical Society, suggests that the winds generated by supermassive black holes could be responsible for accelerating these particles to extreme energies.
At the heart of our Milky Way galaxy lies a black hole called Sagittarius A*, which is currently in a quiet state. But not all black holes are this calm.
Some are active, feeding on massive amounts of surrounding matter—sometimes as much as several suns per year. While most of this matter gets sucked into the black hole, some of it escapes. This escaping material forms powerful winds that blast through space at up to half the speed of light.
These black hole winds have been known for about a decade and are already thought to have a big impact on how galaxies grow, by blowing away gas and preventing the formation of new stars. But Ehlert and Oikonomou think they could also be influencing something much smaller: tiny particles being accelerated to near unimaginable energies.
How powerful are these particles? Oikonomou explains it like this: imagine something smaller than an atom carrying the same amount of energy as a tennis ball served by Serena Williams at 200 kilometers per hour. That’s roughly a billion times more energy than scientists can create in particle accelerators like the Large Hadron Collider. Fortunately, Earth’s atmosphere shields us from these powerful particles. By the time they reach the ground, they’re harmless. But they are a serious concern for astronauts in deep space.
Other theories have tried to explain the origin of these ultra-high-energy cosmic rays. Possibilities include gamma-ray bursts, newborn galaxies, or even other types of black hole activity. But none have been confirmed. Ehlert and Oikonomou’s model suggests that the intense winds from supermassive black holes might be the missing link.
Still, the researchers aren’t claiming victory just yet. The evidence is promising, but not conclusive. Oikonomou describes their conclusion as a cautious “maybe.” Their model does explain a specific feature of these cosmic rays—their unusual chemical makeup at certain energy levels—which other theories can’t. And the team hopes that future neutrino experiments will help test their idea more directly.
For now, the mystery isn’t fully solved. But these new findings add a fascinating piece to the puzzle and show how even the invisible winds from distant black holes might have an impact on the tiny particles flying through our universe.
Source: KSR.
