In 2021, astronomers detected an extraordinarily powerful cosmic ray dubbed Amaterasu. The ray had an energy level of 240 exa-electronvolts, rivaling the most powerful cosmic ray ever recorded in 1991. Despite this incredible energy, the research team behind the discovery was puzzled when they tried to pinpoint the origin of the ray. According to their calculations, Amaterasu came from a quiet corner of space with just a few galaxies – not nearly enough to explain the production of such an energetic ray.
This suggests flaws in our understanding of how cosmic magnetic fields can alter the paths of these rays before they reach Earth. The researchers proposed more exotic explanations like unknown astrophysical phenomena, physical processes beyond the Standard Model of particle physics, or even defects in the structure of spacetime. For now, the origin of these ultra-high-energy cosmic rays remains a mystery. The team plans to upgrade their telescope array to gather more data on these perplexing particles. But whether they’ll detect another ray as powerful as Amaterasu is yet to be seen.