In 1991, the University of Utah's Fly's Eye experiment identified the Oh-My-God particle, an exceptionally high-energy cosmic ray with an origin beyond the Milky Way galaxy. The Telescope Array has since discovered over 30 ultra-high-energy cosmic rays, but none matched the Oh-My-God particle's intensity or origin.
The recent detection of an energetic cosmic ray by the Telescope Array, pointing to a cosmic void, challenges current theories in cosmic ray origins and high-energy physics. This discovery raises intriguing questions about the elusive source of such cosmic phenomena.
Second Highest Cosmic Ray Ever
On May 27, 2021, the Telescope Array experiment identified the second-highest extreme-energy cosmic ray, boasting an energy level of 2.4 x 10^20 electron volts. This single subatomic particle's energy equivalence was illustrated as dropping a brick on your toe from waist height.
The experiment, led by the University of Utah and the University of Tokyo, employed 507 surface detector stations covering 700 km² in Utah's West Desert.
Detected in the north-west region of the Telescope Array, the cosmic ray's trajectory suggested an origin from the Local Void, an empty expanse bordering the Milky Way. Telescope Array co-spokesperson John Matthews emphasized the mystery surrounding these high-energy particles, noting that their trajectories do not lead to known high-energy sources in the sky.
The stuy, titled "An extremely energetic cosmic ray observed by a surface detector array" published in the journal Science, the international collaboration detailed the characteristics of the ultra-high-energy cosmic ray and proposed that its unique features might involve particle physics not yet understood.
They named it the Amaterasu particle, after the Japanese sun goddess, the researchers highlighted the rarity of these events, confirming their authenticity through distinct observation techniques.
John Belz, a professor and study co-author, acknowledged the diverse origins of these high-energy events, speculating on unconventional explanations such as defects in spacetime structure or colliding cosmic strings. The study underscores the intriguing and uncharted aspects of ultra-high-energy cosmic rays, challenging conventional scientific explanations.
Telescope Array Expands for Deeper Cosmic Ray Insights
Cosmic rays, including the rare and powerful Ultrahigh-energy cosmic rays (UHECRs), are subatomic particles from space with energies exceeding 1 EeV-outstripping human-made particle accelerators by a millionfold.
Believed to originate from energetic cosmic phenomena like black holes and gamma-ray bursts, the precise physics and acceleration mechanisms of UHECRs remain elusive. Their infrequent occurrence, estimated at less than one particle per century per square kilometer, necessitates advanced instruments for detection.
Positioned strategically at an elevation of approximately 1,200 meters in Utah's West Desert, the Telescope Array holds a unique advantage in identifying ultra-high-energy cosmic rays.
Benefiting from optimal atmospheric conditions-dry air to prevent ultraviolet light absorption and dark skies to minimize light pollution-the telescope's expansion, featuring 500 new scintillator detectors covering 2,900 km² (1,100 mi²), aims to unravel the mysteries surrounding these cosmic events by capturing a broader range of cosmic ray-induced particle showers.
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