The Amaterasu particle, named after the
sun goddess in Japanese mythology, was an unexpected
ultra-high-energy cosmic ray
In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray with an energy greater than 1 EeV (1018 electronvolts, approximately 0.16 joules), far beyond both the rest mass and energies typical of other cosmic ray part ...
detected in 2021 and later identified in 2023,
using the
Telescope Array Project observatory in
Utah
Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
, United States. It had an energy exceeding 240
exa-
electronvolt
In physics, an electronvolt (symbol eV), also written electron-volt and electron volt, is the measure of an amount of kinetic energy gained by a single electron accelerating through an Voltage, electric potential difference of one volt in vacuum ...
s (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
The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...
galaxy. The single subatomic particle held energy roughly equivalent to a brick dropping to the ground from waist height.
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."
Previously reported extremely high-energy cosmic ray events include a 320 EeV particle in 1991 (
Oh-My-God particle), a 213 EeV particle in 1993
[ and a 280 EeV particle in 2001.]
See also
* Greisen–Zatsepin–Kuzmin limit
References
Cosmic rays
2021 in science
2021 in Utah
Individual particles
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