Amaterasu, the ultra-energy cosmic ray of unknown origin that just hit the Earth

An ultra-high energy cosmic ray has hit the Earth. It has a million times more energy than the most powerful accelerator ever created by man. Astronomers have observed its trajectory but have not found any object in our galaxy or outside it that could explain its origin.. The discovery by the Osaka Metropolitan University, which has just published Science, seems like the beginning of a science fiction film to which researchers, for the moment, have only managed to give it an apocalyptic title: Amaterasu, the sun goddess of Japanese mythology.

Cosmic rays are charged particles of energy that cross the universe at speeds close to that of light.. Those with low energies are produced by the sun, but those with such high energies are exceptionally rare, so astronomers suggest that they can only come from outside our galaxy, since it would require more energetic environments, such as the surroundings of black holes. giants at the centers of distant galaxies.

“It is known that they originate in very violent phenomena, such as the explosion of a supernova, the collision of two stars, or when a black hole engulfs a cloud of gas, but much is still unknown about their nature and properties,” explains the astronomer and director of the National Astronomical Observatory, Rafael Bachiller.

When we talk about high energy we talk about more than 10 to the power of 18 electron volts or, what is the same, an exaelectron volt (EeV), which is approximately a million times more than what the CERN Large Collider in Geneva can achieve.. Amaterasu had an energy of 244 EeV.

Since it is ionizing radiation, it means that they have enough energy to tear electrons from atoms and ionize them. If they reach satellites, or on Earth, electronic or computer equipment can damage them or cause errors.. But if it reaches a living being, it can damage biological tissue, causing a mutation in the DNA.

Professor Toshihiro Fujii, from the Graduate School of Science and the Nambu Yoichiro Institute of Theoretical and Experimental Physics at Osaka Metropolitan University, and an international team of scientists, have been detecting these rays since 2008 through the Telescope Array experiment.. A detector consisting of 507 stations covering an area of 700 square kilometers in Utah, United States. On May 27, 2021, they detected Amaterasu.

“When I discovered it I thought it must have been a mistake, since it showed a level of energy unprecedented in decades,” says Professor Fujii.. Such an energy level is comparable to that of the most energetic cosmic ray ever observed in history, baptized by scientists with the not at all reassuring name Oh-My-God, which hit the Earth in 1991 with an energy of 320 EeV.

On August 7, 1912, physicist Victor Hess flew a balloon to 5,300 meters, and discovered that at that height there was three times more ionizing radiation than on Earth, so the radiation had to come from outer space.. More than a century later, we still do not know with certainty how they are produced or the sources that originate them.. Amaterasu, at the moment, is as mysterious as the Japanese goddess herself, but there is hope that its detection will pave the way for scientists.

“No promising astronomical object has been identified that matches the direction from which it arrived, which fuels the existence of as yet unknown astronomical phenomena, and physical origins beyond the standard model,” reflects Professor Fujii.

“As they are made up of charged particles, the rays that reach us on Earth have been changing direction following the capricious lines of the magnetic fields that permeate the interstellar medium.. Therefore, to find out their origin, instead of locating cosmic rays directly, we can try to observe some of the effects they cause,” explains Bachiller.

When a single energetic cosmic ray hits the Earth, it typically interacts high in the Earth's atmosphere, undergoing a particle physics reaction with an air atom, breaking the atom apart.. The fragments of the atom that emerge usually have enough energy to, in turn, shatter additional atoms, and so on, forming a shower of energetic subatomic particles.