A high-energy particle fell from space in the form of lightning to the surface of the Earth, but it is not known where it came from.

This may sound like something out of science fiction, but it is a scientific fact. About Amatarasu, A cosmic ray that struck Utah on May 27, 2021 has baffled scientists ever since.

Cosmic rays, also known as cosmic rays, are subatomic particles from space that are extremely high in energy as a result of their high speed.

“When I first discovered this ultra-high energy (UHE) cosmic ray, I thought it was a mistake because it showed unprecedented energy levels in the last three decades,” said researcher Toshihiro Fujii of Osaka Metropolitan University. University (OMU) and lead author of the study will be published in this Friday’s issue Science.

Very high-energy cosmic rays are exceptionally rare; They can reach more than 1018 electron volts (the amount of kinetic energy gained or lost by an electron), or one exaelectron volt (EeV), about a million times more than that achieved by the most powerful accelerators ever built by humans. .

Amaterasu recorded an energy level of 244 EeV. This energy level is comparable to the most energetic cosmic rays ever observed, nicknamed “Oh-My-God”, which had an estimated energy of 320 EeV when detected in 1991.

To detect cosmic rays, Professor Fuji and an international team of scientists have been conducting the Telescope Array Experiment since 2008.

The detector consists of 507 stations covering an area of ​​270 square miles in Utah. It was there that they discovered that Amatarasu had fallen on May 27, 2021.

Professor Fujii and his colleagues named the particles Amaterasu, after the sun goddess who, according to Shinto beliefs, played a decisive role in the creation of Japan.

The Amaterasu particle may be as mysterious as the Japanese goddess. The authors note that given this particle’s exceptionally high energy, it should experience only relatively small deflections by foreground magnetic fields, so its entry path from space is expected to be closely related to its source.

However, the results show that its direction of arrival does not indicate an obvious source galaxy or any other known astronomical object that could be considered a possible source. Instead, it suggests that the particle traveled toward Earth from a void in the large-scale structure of the universe, a region inhabited by very few galaxies.

“No astronomical object has been identified that matches the direction from which the cosmic ray came, suggesting the possibility of new physics beyond the standard model of unknown astronomical phenomena and particle physics,” comments Professor Fujii.

The origin of these high-energy particles baffles scientists.

John Matthews, a research professor at the University of Utah and a collaborator on the telescope array project, said the two large cosmic rays appeared “somewhat random”: tracing their paths, nothing seemed to have enough energy. To create such particles..

The amethyst particle, in particular, appeared to originate from a hollow region at the boundary of the Milky Way, known as the local void.

Both researchers point out that they need more data on cosmic rays of that magnitude to get an answer, as at the moment they only have information from Amethyst and Oh-My-God.

Expanding the telescope array may provide some answers.

Once complete, the 500 new detectors will allow the telescope array to capture a cosmic ray-induced particle shower covering about 1,120 square miles, the size of Rhode Island, according to a University of Utah release.