Researchers in Utah have solved the mystery of a cosmic ray that originated in a galaxy far, far away.
Ryuunosuke Takeshige of Kyoto University and Osaka Metropolitan University's L-INSIGHT
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Astronomers have found an extraordinarily high-energy particle that they think came to Earth from beyond our galaxy, adding mystery to the mysterious sources of intense cosmic rays.
Science released fresh findings on Thursday stating that the energy of this subatomic particle—which is undetectable to the human eye—is the same as the impact of dropping a rock on your toe from waist height. According to the research, it is on par with the most powerful cosmic ray ever discovered, the "Oh-My-God" particle recorded in 1991.
Charged particles known as cosmic rays continually shower Earth from orbit. Although the sun may release low-energy cosmic rays, it is the source of really high-energy rays that stands out. It is believed that they come to Earth from other galaxies and sources outside our galaxy.
"If you hold out your hand, one (cosmic ray) goes through the palm of your hand every second, but those are really low-energy things," said John Matthews, a research professor at the University of Utah and a coauthor of the study.
More like one per square kilometer per century when you reach these really high-energy cosmic rays. You're never going to be able to control it.
The precise sources of these high-energy particles remain unclear, even after years of study. Thought to be associated with the universe's most powerful events like black holes, gamma-ray bursts, and active galactic nuclei, the largest ones seen so far seem to come from spaces devoid of matter, where no extreme astronomical phenomena have occurred.
Keeping tabs on cosmic rays with high energy
The Telescope Array, a cosmic ray observatory in Utah's West Desert, recently observed the particle, which has been dubbed the Amaterasu particle after the sun goddess in Japanese mythology.
Constructed of 507 surface detectors the size of ping pong tables over 700 square kilometers (270 square miles), the Telescope Array began operations in 2008.
The Amaterasu particle, which hit the atmosphere over Utah on May 27, 2021, and rained secondary particles onto the earth, where the detectors caught them, was the largest of more than 30 ultra-high-energy cosmic rays that it has detected, according to the research.
“You can check... at the number of particles that arrived each detector and that tells you what the energy of the primary cosmic ray was," Matthews said.
The event, which had an estimated energy of about 244 exa-electron volts, set off 23 surface detectors. Detected almost 30 years ago, the "Oh My God particle" had a voltage of 320 exa-electron volts.
Simply said, there are billions of gigaelectron-volts in 1 exa-electron volt and billions of electron volts in 1 gigaelectron volt. For the Amaterasu particle, it works out to 244,000,000,000,000,000,000 electron volts. For context, the National Aeronautics and Space Administration reports that the average electron energy in the northern aurora is forty thousand volts.
According to New York University physics professor Glennys Farrar, an ultra-high-energy cosmic ray travels at tens of millions of times the speed of light and has more energy than the most powerful artificial particle accelerator, the Large Hadron Collider.
An area with very strong magnetic fields, similar to a larger version of the LHC but in a more natural setting, is necessary. "The chances of one hitting Earth are tiny," Farrar said via email, adding that the study's excluding criteria made the sources very uncommon and the particles vanished into the wide cosmos.
Atmospheric shielding prevents most particle damage to people, while cosmic rays may sometimes cause computer malfunctions. According to NASA, the particles—and radiation in space in general—pose a higher threat to astronauts because they may affect several biological processes and potentially cause structural damage to DNA.
Unidentified origin
Scientists still don't know where these ultra-high-energy particles come from.
According to Matthews, who is also a co-spokesman for the Telescope Array Collaboration, the two largest cosmic rays ever recorded were "sort of random" when their paths were traced back, and nothing seemed to have the energy to generate such particles. In particular, the Amaterasu particle seemed to have come from the Local Void, a region of space that is completely devoid of matter and lies on the galactic periphery.
It doesn't seem like the two highest-energy events, including the one we recently discovered (the 'Oh-My-God' particle), indicate anything at all. It ought to be anything near by. "Anything really large and violent will go unnoticed by astronomers using visible telescopes," Matthews said.
It seems to have originated in an area that resembles a local wasteland. A vacuum. What on earth is happening now?"
Some answers may be forthcoming from an extension of the Telescope Array. Upon completion, the Telescope Array will be able to catch cosmic ray-induced particle showers across an area roughly the size of Rhode Island, covering 2,900 square kilometers (approximately 1,120 square miles), thanks to 500 more detectors, according to a statement from the University of Utah.
