Scientists may have found the ‘supermassive’ cause of cosmic rays

Supermassive black holes are some of the most powerful engines in the universe. These giants sit at the centers of galaxies, including your own Milky Way, and sometimes become active by pulling in large amounts of nearby matter. When this happens, they don't just swallow stars and gas—they also launch fast-moving winds that blast outward at nearly half the speed of light.

These winds, known as ultra-fast outflows, or UFOs, have long been known to shape galaxies. By blowing gas out of the center, they can slow or even shut down the formation of new stars. But recent research points to an even more thrilling role: these winds might be the missing source of ultra-high-energy cosmic rays, the most energetic particles ever observed in the universe.

UFOs aren’t a new discovery. For over a decade, scientists have tracked them as they shoot out from the regions around active supermassive black holes. These winds carry vast amounts of energy and show up in both jetted and non-jetted black hole systems, meaning they’re a widespread feature in galaxies across the cosmos.

According to observations, these outflows can reach speeds close to 150,000 kilometers per second. They are also strongly ionized and form relatively close to the black hole—typically within a few thousand times the black hole’s own size. That places them near the heart of the chaos, right next to the accretion disc of spiraling gas that feeds the black hole.

For years, scientists thought these winds mainly impacted star formation. But that’s only part of the story. A growing number of researchers now think that UFOs may also be responsible for accelerating tiny atomic particles to incredible energies.

Cosmic rays are not rays at all. They’re particles, mostly protons or atomic nuclei, that fly through space at nearly the speed of light. Some come from inside our galaxy. Others, especially the more energetic ones, seem to arrive from outside. But where they come from and how they get their extreme energy remains one of physics’ greatest puzzles.

Most cosmic rays are already high in energy, but some go even further. These ultra-high-energy cosmic rays (UHECRs) carry more than 10¹⁹ electron volts of energy.

To put that into context, that’s about the same amount of energy as a tennis ball served by a pro athlete like Serena Williams—except the cosmic ray is smaller than an atom. It’s an energy level a billion times greater than what scientists can produce with the world’s most powerful particle accelerators.

Since 1962, scientists have observed these ultra-powerful particles, but no one has nailed down their source. They appear so rarely that even long-term studies struggle to gather enough data. Many suspected that gamma-ray bursts, exploding stars, or jets from black holes could be to blame. But none of these ideas has yet been proven.

Now, scientists from the Norwegian University of Science and Technology (NTNU) may have found the most convincing explanation yet.

Foteini Oikonomou, a physicist at NTNU, and her team—including PhD researcher Domenik Ehlert and postdoctoral fellow Enrico Peretti—believe that the winds from active supermassive black holes might solve the mystery. Their work explores the link between small-scale particles and large-scale cosmic events, a field known as astroparticle physics.

“We suspect that this high-energy radiation is created by winds from supermassive black holes,” said Oikonomou.

That idea builds on earlier models. Peretti and his colleagues had already proposed that protons could be accelerated to several exa-electronvolts (EeV) when UFOs crash into the interstellar medium. The shock from that collision creates the perfect environment for particle acceleration.

According to long-standing theory, the maximum energy a cosmic ray can reach depends on how well magnetic fields can trap it. This process, known as diffusive shock acceleration, means that particles with higher nuclear charges—like iron—can reach even higher energies. These could theoretically be boosted to 100 EeV, placing them in the range of observed UHECRs, as long as they aren’t destroyed in the process.

And this isn’t just theory. A Fermi-LAT satellite analysis of 11 nearby galaxies with active black holes and UFOs detected gamma-ray emissions reaching hundreds of giga-electronvolts (GeV). That’s a strong sign that extreme particle acceleration is happening in those environments.

What makes this theory especially compelling is how well it fits into a known gap in the cosmic ray spectrum.

At lower energies, cosmic rays come from within the Milky Way. At higher energies, they’re believed to be extragalactic. The transition between these two sources includes a puzzling dip known as the “gap.” This gap appears between two features in the energy spectrum called the "knee" and the "ankle." Scientists believe the “knee” marks the upper end of cosmic rays from our galaxy, and the “ankle” signals the start of rays from other galaxies.

AGN UFOs may be the perfect candidate to explain the gap. Their particle energy, chemical makeup, and frequency all line up with what’s missing.

A new study modeled 86 UFO systems to calculate how much energy their winds could deliver. The results suggest that these winds can explain not only the total energy observed but also the mix of elements in UHECRs that other models struggle to replicate.

“This model fits the part of the cosmic ray spectrum that hasn’t been explained well before,” said Ehlert.

While the model checks many boxes, scientists are not yet ready to call the case closed.

“Our answer is more of a cautious ‘maybe,’” Oikonomou said. “We find that the conditions related to these winds align particularly well with particle acceleration. But we are still unable to prove that it is specifically these winds that accelerate the particles behind the high-energy cosmic radiation.”

Their theory is also testable. The team hopes to partner with neutrino observatories to look for supporting evidence. Since high-energy particles often produce neutrinos when they interact with matter or radiation, spotting these could help confirm the model.

“In the years to come, we hope to collaborate with neutrino astronomers to test our hypothesis,” Oikonomou said.

Until then, UFOs remain a leading suspect in the ongoing search for the origins of the universe’s most energetic particles. They may not be the final answer, but they’re the best lead physics has right now.

Research findings are available online in the journal Monthly Notices of the Royal Astronomical Society.

Note: The article above provided above by The Brighter Side of News.

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