Mysterious cosmic ray came from outside our galaxy: scientists are perplexed

Cosmology scientists seeking to understand the mysterious origins of powerful cosmic rays have discovered an extremely rare ultra-high-energy particle that they believe came to Earth from outside the Milky Way galaxy, CNN reports.

The energy of this subatomic particle, invisible to the naked eye, is equivalent to a brick falling on your toe from waist height, according to the authors of a new study published Thursday in the journal Science. The study found that it rivals the single most energetic cosmic ray ever observed, the Oh-My-God particle, which was discovered in 1991.

Cosmic rays are charged particles that travel through space and constantly rain down on Earth, CNN explains. Low-energy cosmic rays can come from the Sun, but extremely high-energy ones are exceptional. It is believed that they come to Earth from other galaxies and extragalactic sources.

“If you stretch out your hand, one cosmic ray passes through your palm every second, but these are really low-energy objects,” said study co-author John Matthews, a research professor at the University of Utah. “When you encounter these really high-energy cosmic rays, it’s more like one per square kilometer per century.” It never passes through your hands.”

Despite years of research, the exact origin of these high-energy particles is still unclear. They are thought to be associated with the most energetic phenomena in the Universe, such as those associated with black holes, gamma-ray bursts and active galactic nuclei, but the largest ones discovered so far appear to originate from voids or empty space. where no violent celestial events took place.

The newly discovered particle, nicknamed the Amaterasu particle after the sun goddess in Japanese mythology, was spotted by a cosmic ray observatory in Utah’s Western Desert known as the Telescope Array.

The telescope array, which became operational in 2008, consists of 507 ping-pong table-sized surface detectors covering 700 square kilometers. According to the study, he observed more than 30 ultra-high-energy cosmic rays, but none of them were larger than the Amaterasu particle that entered the atmosphere over Utah on May 27, 2021, raining secondary particles on the ground, where they were detected by detectors.

“You can look at how many particles hit each detector, and that will tell you what the energy of the primary cosmic ray was,” Matthews said.

The event activated 23 surface detectors with an estimated energy of about 244 exa-electron volts. The “Oh My God” particle, discovered over 30 years ago, measured 320 exaelectronvolts.

For reference, CNN explains, 1 exaelectronvolt is equal to 1 billion gigaelectronvolts, and 1 gigaelectronvolt is equal to 1 billion electronvolts. This would give the Amaterasu particle 244,000,000,000,000,000,000,000 electron volts. By comparison, the typical energy of an electron in an aurora is 40,000 electron volts, according to NASA.

An ultra-high-energy cosmic ray packs tens of millions of times more energy than any man-made particle accelerator, such as the Large Hadron Collider (LHC), the most powerful accelerator ever built, says Glennis Farrar, a professor of physics at New York University.

“What is required is a region with very strong magnetic fields – like a super-sized LHC, but of natural origin. And the conditions required are truly exceptional, so the sources are very, very rare, and the particles are dispersed throughout the vast universe, so the chances of one hitting Earth are slim to none,” Farrar says.

The atmosphere largely protects people from any harmful effects of particles, although cosmic rays sometimes cause computer malfunctions. Particles and cosmic radiation more broadly pose a greater risk to astronauts, potentially causing structural damage to DNA and altering many cellular processes, according to NASA.

The source of these ultra-high energy particles has scientists baffled.

Matthews, co-spokesperson for the Telescope Array Collaboration, said the two largest cosmic rays recorded turned out to be “sort of a fluke” – when their trajectories are traced, there appears to be nothing high enough energy to produce such particles. In particular, the Amaterasu particle appears to have originated from the so-called Local Void, an empty region of space bordering the Milky Way galaxy.

“If you take the two highest energy events – the one we just discovered, the ‘Oh my God’ particle – they don’t even seem to indicate anything. It must be something relatively close. Astronomers with visible telescopes can’t see anything really big or really violent, Matthews said. – It comes from an area that appears to be local empty space. This is emptiness. So what the hell is going on?”

Expanding the telescope array may provide some answers, CNN notes. Once completed, 500 new detectors will allow the telescope to detect particle flows caused by cosmic rays over an area of ​​2,900 square kilometers (about 1,120 square miles) – an area almost the size of Rhode Island, according to a statement from the University of Utah.