Get to know Amaterasu, the High Cosmic Ray that Hit the Earth and the Mystery of Its Origin

Amaterasu particles are estimated to have an energy of 244 EeV (Osaka Metropolitan University/L-Insight, Kyoto University/Ryuunosuke Takeshige)

Cosmic rays are highly energetic subatomic particles, moving through space at close to the speed of light. They can come from various sources, both from the Sun and objects outside our solar system.

When these cosmic rays collide with the Earth’s atmosphere, they break apart into jets of other particles. The first discovery of cosmic rays was made by Austrian physicist Victor Hess in 1912. These observations were made using a hydrogen balloon to measure atmospheric radiation with an electroscope.

The Telescope Array, located outside Delta, Utah, consists of more than 500 surface detectors that form a square grid spanning 270 square miles. Since starting operations, the Telescope Array has detected more than 30 UHECRs.

On May 27, 2021, this detector identified Amaterasu, an extraordinary event announced after careful analysis at a fall conference and recently published in the journal Science.