Earth was just struck by an extremely powerful cosmic ray and we don’t know where it came from

In a groundbreaking discovery that has left astrophysicists astounded, a cosmic ray with an energy exceeding 240 exa-electron volts, named Amaterasu, struck Earth’s atmosphere. This event is second only to the 1991 detection of the Oh-My-God particle, which had an energy of 320 exa-electron volts. The origin of these ultra-high-energy cosmic rays remains an enigma, challenging our current understanding of astrophysical phenomena. Cosmic rays, primarily composed of atomic nuclei and sub-nuclear particles like protons and electrons, travel through the universe at near-light speeds, carrying more energy than theoretically expected. While lower-energy cosmic rays are understood to originate from stars and supernovas, the sources of these ultra-high-energy rays are elusive. Our atmosphere shields us from direct impact, but when these rays collide with atmospheric particles, they create a cascade of secondary particles detectable by observatories on Earth. The Telescope Array, an extensive observatory covering 700 square kilometers, detected the Amaterasu particle on May 27, 2021. This discovery, made using advanced detection techniques, confirmed that such high-energy cosmic events are not anomalies but real astrophysical occurrences. The naming of the particle after the Shinto sun goddess reflects its extraordinary nature. One of the most baffling aspects of these cosmic rays is their untraceable origins. Theoretically, their high energy should allow for a clear path back to their source. However, both the Oh-My-God particle and Amaterasu seem to originate from regions in space that lack sufficiently energetic phenomena to produce them. This discrepancy suggests unknown mechanisms or sources at play in the cosmos. Ultra-high-energy cosmic rays like Amaterasu pose a significant puzzle due to the Greisen-Zatsepin-Kuzmin (GZK) limit, an estimated maximum energy threshold for cosmic rays traveling long distances. Amaterasu’s energy exceeds this limit, indicating that its source should be within 160 million light-years. Yet, no known astrophysical event within this range seems capable of generating such energy. Tracing Amaterasu’s trajectory leads back to a cosmic void, a relatively empty space between galaxy clusters. This finding intensifies the mystery, as such voids are unlikely to house phenomena capable of producing ultra-high-energy cosmic rays. This gap in understanding points to potential new astrophysical phenomena or previously unrecognized capabilities of cosmic magnetic fields.