The secret of Amaterasu: the cosmic ray challenging the limits of knowledge.
Recently, Earth has been struck by a cosmic ray from outer space, a discovery announced by Toshihiro Fujii’s team at Osaka Metropolitan University. This phenomenon has been documented in the journal Science, and the ray has been nicknamed Amaterasu, in honor of the Japanese sun goddess.
Amaterasu boasts an extraordinarily high energy level, surpassing even that generated by the CERN’s Large Hadron Collider in Geneva, the most powerful particle accelerator in the world. Its energy reaches 240 exa-electron volts, making it the second most powerful ray ever discovered, following the 1991 ray called “Oh my God,” with its 320 exa-electron volts.
In an attempt to explain this event, the scientific team has explored various hypotheses, ranging from the most conventional explanations to more extreme theories. Amaterasu represents the fourth particle of this kind detected by terrestrial instruments from outer space, but its precise origins remain unknown.
Cosmic rays, despite their name sounding like science fiction, are high-energy subatomic particles traveling through space at speeds close to that of light. They can originate from galactic or extragalactic sources, or even from our own Sun. The peculiarity of the ray that hit Earth on November 27 lies mainly in its extraordinary speed and extremely high energy values, which greatly complicate its detection.
Ultra-high-energy cosmic rays surpass the exa-electron volt, a measurement nearly a million times higher than the energy reached by particles in the most powerful accelerator built by humans. Those that exceed 200 exa-electron volts are extremely rare, reaching Earth approximately once every century, one per square kilometer. So far, only four of such events have been recorded, adding further difficulties to understanding their origins.
Amaterasu was detected thanks to the sensors of the Telescope Array, but all efforts to determine its origin have been futile so far. It is only known that its source is extragalactic, coming from a region of the cosmos outside our galaxy, although in its vicinity. The analyses conducted by scientists have deepened the mystery, as calculations based on the movement of cosmic rays and their interactions with the magnetic fields of celestial objects have not revealed anything significant in the source area.
Nevertheless, the hypothesis of a black hole remains the most plausible according to current knowledge. According to John Belz from the University of Utah, co-author of the article in Science, it could be an undetected supermassive black hole due to a magnetic field that deflected the incoming particle. Scientists admit that current models of cosmic rays may be partly incorrect, and Amaterasu could originate from a different region of the cosmos with clearer explanations.
However, they do not exclude the possibility of unknown physical phenomena. Some more intriguing hypotheses include the possibility that the cosmic ray was caused by a defect in the space-time structure or a collision of cosmic strings. Experts describe these as “almost crazy ideas,” expecting further precise investigations in the hope of unraveling the mystery.