Amaterasu particle

{{Short description|Ultra-high-energy cosmic ray}}

The Amaterasu particle, named after the sun goddess in Japanese mythology, was an unexpected ultra-high-energy cosmic ray detected in 2021 and later identified in 2023,{{Cite journal |last1=Telescope Array Collaboration |last2=Abbasi |first2=R. U. |last3=Allen |first3=M. G. |last4=Arimura |first4=R. |last5=Belz |first5=J. W. |last6=Bergman |first6=D. R. |last7=Blake |first7=S. A. |last8=Shin |first8=B. K. |last9=Buckland |first9=I. J. |last10=Cheon |first10=B. G. |last11=Fujii |first11=T. |last12=Fujisue |first12=K. |last13=Fujita |first13=K. |last14=Fukushima |first14=M. |last15=Furlich |first15=G. D. |date=2023-11-24 |title=An extremely energetic cosmic ray observed by a surface detector array |journal=Science |language=en |volume=382 |issue=6673 |pages=903–907 |doi=10.1126/science.abo5095 |pmid=37995237 |arxiv=2311.14231 |bibcode=2023Sci...382..903T |s2cid=265381136 |issn=0036-8075}} using the Telescope Array Project observatory in Utah, United States. It had an energy exceeding 240 exa-electronvolts (EeV) and was inferred through the two dozen particles it sent toward ground detectors. This single particle appears to have emerged, inexplicably, from the Local Void, an empty area of space bordering the Milky Way galaxy.{{cite journal |first1=Hannah |last1=Devlin |title='What the heck is going on?' Extremely high-energy particle detected falling to Earth. |journal=The Guardian |url=https://www.theguardian.com/science/2023/nov/24/amaterasu-extremely-high-energy-particle-detected-falling-to-earth |date=2023-11-24 |access-date=November 24, 2023 |archive-date=November 24, 2023 |archive-url=https://web.archive.org/web/20231124093358/https://www.theguardian.com/science/2023/nov/24/amaterasu-extremely-high-energy-particle-detected-falling-to-earth |url-status=live }} The single subatomic particle held energy roughly equivalent to a brick dropping to the ground from waist height.{{Cite web |last=Hunt |first=Katie |date=2023-11-23 |title=Scientists detect a cosmic ray that's almost as powerful as the 'Oh-My-God' particle |url=https://www.cnn.com/2023/11/23/americas/powerful-cosmic-ray-amaterasu-particle-detected-scn/index.html |access-date=2023-12-07 |website=CNN |language=en}}

According to study leader, Associate Professor Toshihiro Fujii from Osaka Metropolitan University, "No promising astronomical object matching the direction from which the cosmic ray arrived has been identified, suggesting possibilities of unknown astronomical phenomena and novel physical origins beyond the Standard Model."{{cite journal|first1=Evrim |last1=Yazgin |title=Second OMG cosmic ray particle breaks physics again|journal=Cosmos|url=https://cosmosmagazine.com/space/astrophysics/second-largest-cosmic-ray-particle/#:~:text=The%20ultra%20high-energy%20cosmic%20ray%20was%20named%20%E2%80%9CAmaterasu%2C%E2%80%9D,in%20a%20paper%20published%20in%20the%20journal%20Science.|date=2023-11-24|access-date=November 24, 2023|archive-date=November 24, 2023|archive-url=https://web.archive.org/web/20231124121233/https://cosmosmagazine.com/space/astrophysics/second-largest-cosmic-ray-particle/#:~:text=The%20ultra%20high-energy%20cosmic%20ray%20was%20named%20%E2%80%9CAmaterasu%2C%E2%80%9D,in%20a%20paper%20published%20in%20the%20journal%20Science.|url-status=live}}

Previously reported extremely high-energy cosmic ray events include a 320 EeV particle in 1991{{Cite journal |last=Conroy |first=Gemma |date=2023-11-23 |title=The most powerful cosmic ray since the Oh-My-God particle puzzles scientists |url=https://www.nature.com/articles/d41586-023-03677-0 |journal=Nature |language=en |doi=10.1038/d41586-023-03677-0|pmid=37996738 |s2cid=265403953 }} (Oh-My-God particle), a 213 EeV particle in 1993{{Cite book |last1=Sasaki |first1=N |title=Proceedings of the 27th International Cosmic Ray Conference ICRC2001 |last2=et |first2=al |publisher=Copernicus-Gesellschaft |year=2001 |pages=337}} and a 280 EeV particle in 2001.{{Cite journal |last1=Hayashida |first1=N. |last2=Honda |first2=K. |last3=Honda |first3=M. |last4=Imaizumi |first4=S. |last5=Inoue |first5=N. |last6=Kadota |first6=K. |last7=Kakimoto |first7=F. |last8=Kamata |first8=K. |last9=Kawaguchi |first9=S. |last10=Kawasumi |first10=N. |last11=Matsubara |first11=Y. |last12=Murakami |first12=K. |last13=Nagano |first13=M. |last14=Ohoka |first14=H. |last15=Takeda |first15=M. |date=1994-12-26 |title=Observation of a Very Energetic Cosmic Ray Well Beyond the Predicted 2.7 K Cutoff in the Primary Energy Spectrum |url=https://link.aps.org/doi/10.1103/PhysRevLett.73.3491 |journal=Physical Review Letters |language=en |volume=73 |issue=26 |pages=3491–3494 |doi=10.1103/PhysRevLett.73.3491 |pmid=10057397 |bibcode=1994PhRvL..73.3491H |issn=0031-9007}} This makes the Amaterasu particle the third most powerful cosmic ray to have been detected.