Artist’s illustration of a massive air shower caused by ultra-high energy cosmic rays.Credit: Toshihiro Fujii/L-INSIGHT/Kyoto University
The astronomers involved were telescope array An experiment conducted in the western desert of Utah has detected ultra-high energy cosmic rays (UHECR) with an energy level of 244 EeV. new paper Published in Science magazine. This is the most energetic cosmic ray detected since 1991, when astronomers detected so-called cosmic rays. “Oh my God” particle, with an even more impressive 320 EeV of energy. Astronomers have named this latest event the “Amaterasu” particle. Shinto sun goddess It is said that he created Japan. You could also call it the “Oh-My-Goddess” particle.
Cosmic rays are high-energy elementary particles that travel through space at speeds close to the speed of light. Technically, cosmic rays It is simply an atomic nucleus made up of protons or clusters of protons and neutrons. Most come from the Sun, but some come from objects outside our solar system. When these rays hit Earth’s atmosphere, they break up into a shower of other particles (both positively and negatively charged).
they were first discovered by an Austrian physicist in 1912 victor hess A hydrogen balloon makes a series of ascents, and an electroscope measures radiation in the atmosphere. He discovered that the ionization rate was three times higher than at sea level, thereby disproving the competing theory that this radiation came from Earth’s rocks.So far I could see the fog room At the Science Museum, cosmic ray trails look like wispy little white lines, similar to the contrails of a small jet plane.
Cosmic rays come in a wide range of energies, with the most common being lower energies. These are the cosmic rays Hess detected and are the ones most likely to appear in the museum’s cloud chamber. There is a theoretical limit to the energy of cosmic rays, proposed in 1965. From Earth he is less than 50 EeV coming from more than 300 million light years away. It is due to the cosmic microwave background radiation, which was discovered in 1964 and is the afterglow of the Big Bang that spreads throughout the universe. Cosmic rays that travel farther than that will be destroyed by interaction with the CMB before they reach Earth’s detectors. This is known as his GZK cutoff after the scientists who proposed it (Kenneth Greisin, Georgiy Zatsepin, and Vadim Kuzmin).
Osaka Metropolitan University/L-INSIGHT/Kyoto University/Ryuunosuke Takeshige/CC BY-NC-SA
The discovery in 1991 of the “Oh my God” particle cast doubt on that prevailing theory, suggesting that it crashed into Earth’s atmosphere at speeds very close to the speed of light and came from the direction of the constellation Perseus in the northern hemisphere. It carried the energy equivalent of a bowling ball dropped from shoulder height, packed tightly into subatomic particles. Astronomers detected dozens of UHECR phenomena over the next several decades, but nothing comparable has been found since then.
But what is the source of UHECR that can accelerate subatomic particles to such incredible speeds? Not even a supernova could do this. One possible cause is an expanding shock wave from a cosmic explosion. For example, a black hole tears apart a star and generates a massive jet of plasma. Particles cross magnetic fields over and over again, picking up energy as they move through space. . Another candidate is an active galactic nucleus (AGN), which typically resides at the center of a galaxy and is thought to contain a supermassive black hole. AGNs produce powerful jets of superheated plasma accompanied by shock waves.
Other suggestions include gamma-ray bursts (which themselves originate from unknown sources) and regions of intense star formation known as starburst galaxies. It doesn’t help that UHECR’s orbit is bent by magnetic fields on its way to detectors on Earth. This makes it difficult to reconstruct the route traveled by UHECR and locate the empty origin. Astronomers thought they had identified some interesting hotspots in 2017. One was in the constellation Centaurus A, and the other was in a galaxy called M82 in the constellation Ursa Major. However, confidence in the former hotspot has waned since 2019, as the number of UHCERs detected from it appears to be decreasing.
Animation of recorded signals and events of a highly energetic particle called the “Amaterasu” particle. Credit: Osaka Metropolitan University/CC BY-SA
The telescope array consists of more than 500 surface detectors arranged in a square grid covering approximately 270 square miles (700 square kilometers) outside Delta, Utah. Since the start of operations, more than 30 UHECRs have been recovered. Still, co-author Toshihiro Fujii of Osaka Metropolitan University in Japan says:I thought there must have been a mistake.” When the “Amaterasu” particle was detected in an experiment on May 27, 2021. As the saying goes, extraordinary claims require extraordinary evidence, so the detection and trajectory analysis were not presented until last fall’s conference, and the paper was only published now. Appearing in Science.
Like its 1991 predecessor, astronomers are puzzled as to where this particle came from. Their trajectory took them to an empty region of space known as the “Local Void” adjacent to the Milky Way. “The particles are so high-energy that they shouldn’t be affected by galactic and extragalactic magnetic fields. We should be able to point to where in the sky they came from.” Co-author John Matthews said:, University of Utah Telescope Array Co-Spokesperson. “But in the case of the Oh My God particle and this new particle, even if we trace its trajectory back to its source, there’s nothing high enough energy to produce it. That’s the mystery of this case – what the heck? Is that happening?”
We may learn more once astronomers complete the expansion of the telescope array, adding 500 new scintillator detectors, increasing the detection area to 1,100 square miles (2,900 square kilometers). This should increase the frequency of detecting such UHECRs.
“These events seem to come from completely different parts of the sky. There’s no single mysterious source.” Co-author John Beltz said:, and is also collaborating with the University of Utah. “It could be that there’s a flaw in the fabric of space-time and cosmic strings are colliding. So I’m just spewing out crazy ideas that people come up with because there’s no conventional explanation.” The magnetic field is probably stronger than we think, but that doesn’t agree with other observations showing that the field is not strong enough to produce significant curvature at these 10-20 electron volt energies. It’s really a mystery.”
DOI: Science, 2023. 10.1126/science.abo5095 (About DOI).
Posted images by Osaka Metropolitan University/L-INSIGHT, Kyoto University/Ryuunosuke Takeshige
