A potent cosmic ray named ‘Amaterasu’ has struck the Earth, marking one of the most forceful cosmic events observed, leaving scientists puzzled about its origin and nature. This highly energetic particle, christened after a Japanese deity, arrived from a region in space where little is known to exist, as per recent findings.
Cosmic rays, comprising mainly protons or helium nuclei, incessantly traverse the vast expanse of the universe. Among them, a small subset, referred to as “ultrahigh-energy cosmic rays,” possess astonishing energy levels surpassing even the most intense phenomena known in the cosmos. These exoenergetic particles, with energies exceeding one exaelectronvolt (EeV), are approximately a million times more energetic than particles accelerated in man-made accelerators.
On May 21, 2021, scientists detected one of these supercharged cosmic rays using the Telescope Array project, covering over 270 square miles in Utah with individual substations. This particle boasted an immense energy of 244 EeV, ranking as the most energetic cosmic ray detected since the 1991 discovery of the ‘Oh My God’ (OMG) particle, which soared at 320 EeV, traveling faster than 99.9% of the speed of light.
A forthcoming study in the journal Science, authored by researchers from Osaka Metropolitan University (OMU), details this recent cosmic ray, dubbed “Amaterasu” in homage to the sun goddess of the Shinto faith, believed to have played a role in Japan’s creation.
The cosmic ray’s source remains elusive. “Its direction of arrival indicates a gap in the large-scale structure of the Universe,” wrote the researchers in Science. This region lacks known galaxies, nebulae, or cosmic structures, raising questions about its origin.
Speculation arises about whether magnetic fields surrounding massive celestial bodies might have deflected the cosmic ray toward Earth. However, unlike their less energetic counterparts, ultrahigh-energy rays are less likely to experience deflection, noted the researchers.
The origin of such a powerful cosmic event remains uncertain. Potential sources proposed by researchers include supernova explosions, black hole mergers, and pulsars. However, the ‘Amaterasu’ particle might also originate from uncharted astronomical phenomena or novel physical principles extending beyond the Standard Model of physics, suggested Fujii.
Similar mysteries shroud the OMG particle detected in 1991, leaving researchers striving to unveil the mechanisms behind these enigmatic events. The team anticipates that upcoming observatories with advanced capabilities will shed light on the origins and causes of these ultrahigh-energy particles.