The second highest-energy cosmic ray ever detected

The particles are so high energy, they shouldn’t be affected by galactic and extra-galactic magnetic fields.


The Telescope Array experiment discovered the second-highest extreme-energy cosmic ray on May 27, 2021. This single subatomic particle has an energy of 2.4 x 1020eV. 

The Telescope Array, led by the University of Utah (the U) and the University of Tokyo, is made up of 507 surface detector stations spread out in a square grid covering 700 km2 (~270 miles2) in the West Desert of the state, just west of Delta, Utah. The event splattered across 48 km2 (18.5 mi2) and activated 23 detectors in the northwest area of the Telescope Array. It arrived from the Local Void, the empty region of space that abuts the Milky Way galaxy.

Because of their immense energy, the galactic and extra-galactic magnetic fields shouldn’t affect the particles. You ought to be able to identify their origin in the sky.

John Matthews, Telescope Array co-spokesperson at the U and co-author of the study, said, “But in the case of the Oh-My-God particle and this new particle, you trace its trajectory to its source, and there’s nothing high energy enough to have produced it. That’s the mystery of this—what is going on?”

The highest-energy cosmic ray ever seen was discovered in 1991 by the University of Utah Fly’s Eye experiment. The cosmic ray’s energy, later dubbed the “Oh-My-God particle,” stunned astrophysicists. The particle had more power than could be expected from cosmic rays coming to Earth from distant galaxies, and nothing in our galaxy could have produced it. The particle shouldn’t exist.

Since then, the Telescope Array has recorded over thirty ultra-high-energy cosmic ray observations; nevertheless, none of them have reached the energy of an Oh-My-God. As of yet, no observations have been made that shed light on their origin or mode of travel to Earth.

About the second highest-energy cosmic ray ever, an international team of scientists characterizes the ultra-high-energy cosmic ray, assesses its properties, and concludes that the rare phenomenon may result from particle physics that science has yet to discover. In Japanese mythology, Scientists called it the Amaterasu particle after the sun goddess. Different observation techniques were used to identify the Oh-My-God and Amaterasu particles, indicating that these ultra-high energy events are actual despite their rarity.

They come from entirely different places in the sky. It’s not like there’s one mysterious source.

John Belz, professor at the U and co-author of the study, said“It could be defects in the structure of spacetime, colliding cosmic strings. I mean, I’m just spit-balling crazy ideas that people are coming up with because there’s no conventional explanation.”

The findings are published in the Journal of Science.


See stories of the future in your inbox each morning.