The Northern Lights, which occur when particles from the Sun enter the Earth’s atmosphere, generate brilliant sky displays in our Northern Hemisphere, offering an occasional cosmic show enjoyed by millions.
But how collisions between these particles, or low-energy cosmic rays, and the Earth’s gases result in the Northern Lights are less well-understood.
Even more puzzling are collisions involving high-energy cosmic rays, which possess more than one million times the energy than those from the Sun and emanate from exploding stars, or supernovae. Scientists have typically relied on computer simulations to unpack their collision with Earth’s atmosphere, but these methods have produced varied, and sometimes conflicting, results.
New research by an international team of physicists takes an unprecedented approach that offers a clearer understanding of these interstellar wonders.
Using CERN’s Large Hadron Collider, the scientists have recreated how high-energy cosmic rays enter the Earth’s atmosphere and collide with our planet’s gases.
The results, reported in the journal Physical Review Letters , help decipher the origins of interstellar particles from the cosmos.
“We now have a better understanding of how particles from objects more exotic than the Sun interact with our atmosphere,” says Jesse Liu, a New York University assistant professor of physics who led the research. “By advancing our knowledge of high-energy cosmic collisions in the Earth’s atmosphere, we have taken another step to unraveling the many mysteries of our universe.”
“The published results are indeed something special because these data are unique, and in our measurements, we were able to show that our previous models for this type of interaction are actually very inaccurate,” adds Cigdem Issever, a physicist at Humboldt-University of Berlin and one of the paper’s authors.
Recognizing the limitations of computer simulations, Liu, Issever, and their colleagues, who included scientists from Hamburg’s DESY Research Center, turned to the Large Hadron Collider (LHC)—the world’s most powerful particle physics machine, located outside of Geneva—to devise an innovative experiment that mimics how high-energy cosmic rays collide with the Earth’s atmosphere.
Focusing on oxygen’s foundational role in Earth’s atmosphere, the scientists introduced oxygen beams for the first time in the LHC and collided them with LHC-generated proton beams, which replicate the cosmic rays that emanate from supernovae. The results constituted the world’s first measurements of cosmic rainstorms recreated in controlled-lab conditions.
The researchers took millions of closeup photos of these outcomes using a 100-million-pixel camera that captures the aftermath of proton collisions that occur up to 40 million times per second.
Part of CERN’s ATLAS collaboration, which is exploring the fundamental nature of matter and the basic forces that shape the universe, the sophisticated device measured the number, energies, and angles of particles made in the proton-oxygen collision to offer precise portraits of the birth of these cosmic rainstorms.
“These new results significantly sharpen our knowledge of these subatomic interactions and will help us further explore the nature of cosmic particles raining from the sky,” concludes Liu.
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Physical Review Letters
Measurement of Charged-Particle Production in √𝑠NN =9.62 TeV Proton-Oxygen Collisions as a Probe of Cosmic-Ray Air Showers with the ATLAS Detector
14-Sep-2026