The telescope array experiment detected a high-energy cosmic ray with a surface detector, but the direction of the ray’s arrival showed no clear evidence, the researchers report.
According to the results The study was published Nov. 23 in the journal ScienceAn unusually high-energy cosmic ray arrived on May 27, 2021, with a calculated energy of about 244 exaelectron volts (EeV).
The authors note that given the particle’s exceptionally high energy, it should undergo only relatively small deflections by forward magnetic fields, so its direction of arrival is expected to be very closely related to its source. However, the results show that its direction of arrival shows no clear evidence of a galaxy or any other known astronomical object.
Cosmic rays are energetically charged particles originating from sources inside or outside the galaxy. Very high-energy cosmic rays are extremely rare, and their energy reaches 1018 electron volts, or exa-electron volts, about a million times greater than that achieved by the most powerful accelerators ever built by humans.
Study co-researcher John Matthews, a professor of astrophysics at the University of Utah in the US, said the observed particle has an enormous amount of energy, but is contained in a very small body. Cosmic rays consist of protons and nuclei that travel through space at a wide range of energies, he explained in a report by al-Arabi al-Jadith. When a cosmic ray hits Earth, it hits the nucleus of an atom in the atmosphere, creating a layer of other particles that can be detected on Earth’s surface.
Whatever their source, the particles must come from a relatively close cosmic neighborhood. This is because high-energy cosmic rays lose energy as they travel, interacting with the cosmic microwave background, which is the afterglow of the Big Bang.
To detect such rays from space, the special cosmic ray detector has 507 surface scintillator stations, covering a wide detection area of 700 square kilometers in Utah, using more than 500 detectors made of plastic scintillators. Emits light when it collides with a charged particle.
“On May 27, 2021, we discovered a particle with a massive energy level of 244 electron volts. When I first discovered this ultra-high-energy cosmic ray, I thought there must be a mistake because it showed unprecedented energy levels. Over the past three decades,” says the researcher.
This energy level is similar to a very energetic cosmic ray called the Oh-My-God particle, which had an energy of 320 MeV when it was discovered in 1991.
Among several candidates for a name for the newly discovered particle, the research team settled on calling it “Amaterasu,” after the sun goddess who, according to Shinto theory, played a fundamental role in the founding of Japan.
“No astronomical object has been identified that matches the direction the newly discovered cosmic ray came from, suggesting unknown astronomical phenomena and new physics outside the standard model,” says the study’s co-author. “In the future, we are committed to continuing to operate the Telescope Array Experiment, where, with our current experiment enhanced with quadruple sensitivities called TAx4, the next generation of observatories will begin a detailed investigation of the source of this highly energetic particle,” he adds.
Finding the sources of cosmic rays has often been a challenge for scientists. For example, let’s go back to last June when scientists discovered a mysterious radiation called Hawking radiation (after the late British physicist Stephen Hawking). At that time, it became clear that the source was black holes.
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