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Space scientists trying to understand the mysterious origins of powerful cosmic rays have detected an extremely rare, ultra-high-energy particle that they believe came to Earth from beyond the Milky Way galaxy.
The energy of this subatomic particle, invisible to the naked eye, is equivalent to dropping a brick from waist height onto your toe, according to the authors of the new study published Thursday in the journal Science. According to the study, this particle rivals the “Oh My God” particle detected in 1991, which is the most energetic cosmic ray ever observed.
Cosmic rays are charged particles that travel through space and constantly rain down on Earth. Low-energy cosmic rays can be emitted from the sun, but extremely high-energy ones are the exception. They are thought to have traveled to Earth from other galaxies and extragalactic sources.
“If you hold out your hand, a cosmic ray passes through your palm every second, but they’re really low-energy things,” said study co-author John Matthews, a research professor at the University of Utah.
“When you get to these really high energy (cosmic rays), it’s more like one per square kilometer per century. It never goes out of your hands.
Despite years of research, the exact origins of these high-energy particles are still unclear. These are thought to be associated with the most energetic events in the universe, such as black holes, gamma-ray bursts and active galactic nuclei, but the largest discovered so far appear to originate in voids, or empty space, where violent celestial bodies are absent. events happened.
Tracking high energy cosmic rays
The recently discovered particle, called the Amaterasu particle after the sun goddess in Japanese mythology, was detected by a cosmic ray observatory known as the Telescope Array in Utah’s Western Desert.
The Telescope Array, which became operational in 2008, consists of 507 ping-pong table-sized surface detectors covering 700 square kilometers (270 square miles).
More than 30 ultra-high-energy cosmic rays have been observed, but none larger than the Amaterasu particle that hit the atmosphere over Utah on May 27, 2021, showering secondary particles where they were caught by detectors. study.
“You can look at how many particles hit each detector, and that tells you what the energy of the primary cosmic ray was,” Matthews said.
The event triggered 23 surface detectors with a calculated energy of approximately 244 exa-electron volts. The “Oh God particle” detected more than 30 years ago was 320 exa-electron volts.
For reference, 1 exa-electron-volt equals 1 billion gigaelectron-volts, and 1 gigaelectron-volt equals 1 billion electron-volts. This makes the Amaterasu particle 244,000,000,000,000,000,000 electron volts. By comparison, the typical energy of an electron in a polar aurora is 40,000 electron volts, according to NASA.
An ultra-high-energy cosmic ray carries tens of millions of times more energy than any man-made particle accelerator, such as the Large Hadron Collider, the most powerful accelerator ever built, explained Glennys Farrar, a professor of physics at New York University.
“What’s required is a region of very high magnetic fields, like a super-sized LHC, but natural. And the conditions required are truly extraordinary, so the resources are very, very rare and the particles are scattered across the vast universe, so the chance of one of them hitting Earth is very small.” ” he said in the email.
The atmosphere largely protects people from the harmful effects of particles, but cosmic rays sometimes cause computer malfunctions. According to NASA, particles, and space radiation more generally, pose a greater risk to astronauts with the potential to cause structural damage to DNA and alter many cellular processes.
mysterious source
The source of these ultra-high-energy particles baffles scientists.
Matthews, co-spokesperson for the Telescope Array Collaboration, said the two largest recorded cosmic rays appeared “kind of random” and that when their trajectories were traced back, there was nothing high enough energy to produce such particles. The Amaterasu particle specifically appeared to originate from what is known as the Local Void, an empty area of space surrounding the Milky Way galaxy.
“If you take the two highest-energy events – the ‘Oh My God’ particle we just found – they don’t seem to indicate anything. It must be something relatively close. “Astronomers with visible telescopes can’t see anything really big and violent,” Matthews said.
“He comes from an area that looks like a local wasteland. This is a gap. So what’s going on?
Expanding the Telescope Array may provide some answers. Once completed, the 500 new detectors will allow the Telescope Array to capture showers of cosmic ray-induced particles across 2,900 square kilometers (about 1,120 square miles) — an area nearly the size of Rhode Island, according to a University of Utah statement.
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