Researchers have detected one of the highest-energy particles ever falling to Earth. Cosmic rays are high-energy particles that come from sources in space such as the sun, but this recent detection is more powerful than anything that can be explained by known sources in our galaxy or even beyond. The particle had an energy of 2.4 x 1020eV, which is millions of times the energy of the particles produced in a particle collider.
The detection was made in May 2021 using a facility called the Telescope Array, located near Salt Lake City in Utah. It has 500 surface detectors which are spread over 300 square miles of desert, designed to detect cosmic ray events. It has observed more than 30 ultra-high-energy cosmic rays since 2007, but this was the most powerful one detected so far.
It is the second most powerful cosmic ray ever detected, only beaten out by one detected in 1991 which was named the Oh-My-God particle. The strange thing about these events is that the researchers have no idea where they are coming from.
“The particles are so high energy, they shouldn’t be affected by galactic and extra-galactic magnetic fields. You should be able to point to where they come from in the sky,” said one of the researchers, John Matthews of the University of Utah, in a statement. “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 the heck is going on?”
Even a big event like a supernova would be nowhere near powerful enough to produce particles like this, and the particle seemed to come from an empty area of space on the edge of the Milky Way called the Local Void. “These events seem like they’re coming from completely different places in the sky. It’s not like there’s one mysterious source,” said another of the researchers, John Belz. “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 not a conventional explanation.”
The researchers hope to use upcoming facilities like an expansion to the Telescope Array to find and study more of these events and learn about their possible source. “It’s a real mystery,” said Belz.
The research is published in the journal Science.
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