Astronomers at the Telescope Array experiment in Utah have detected an ultra-high-energy cosmic ray (UHECR) with a record-breaking energy level of 244 EeV, marking the most energetic cosmic ray since 1991. The particle, named Amaterasu (after the Shinto sun goddess), was identified through a complex trajectory analysis, leading researchers to an empty area of space known as the “Local Void.”
Cosmic rays are highly energetic subatomic particles that travel near the speed of light through space. They consist of atomic nuclei, primarily protons or clusters of protons and neutrons. The 1991 discovery of the “Oh-My-God” particle, with an energy level of 320 EeV, challenged prevailing theories about the theoretical limit of cosmic ray energy proposed in 1965.
The recent detection poses challenges in explaining the source of such ultra-high-energy cosmic rays. Potential sources include cosmic-scale explosions, such as black hole events or active galactic nuclei (AGNs) with supermassive black holes at their centers. However, the trajectories of UHECRs are influenced by magnetic fields, making it challenging to pinpoint their origin in the sky accurately.
The Telescope Array, consisting of over 500 surface detectors in Utah, has picked up more than 30 UHECRs since its inception. The latest discovery raises questions about the conventional explanations for cosmic ray origins. Researchers are exploring various theories, from defects in the structure of spacetime to colliding cosmic strings.
Illustration of ultra-high-energy cosmic ray astronomy to clarify extremely energetic phenomena. (Image: Osaka Metropolitan Univ./L-INSIGHT/Kyoto Univ./Ryuunosuke Takeshige/CC BY-NC-SA)
The ongoing expansion of the Telescope Array, adding 500 new scintillator detectors, aims to increase the detection area to 1,100 square miles. This expansion could lead to more frequent detections of UHECRs, providing further insights into these mysterious and ultra-energetic cosmic phenomena. The current mystery surrounding the origin of Amaterasu and similar particles highlights the need for continued research and exploration in the field of astrophysics.
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