Scientists Detect Most Powerful Cosmic Ray in Decades, Origin Remains a Mystery

The discovery of an ultra-energetic cosmic ray poses questions about its source and the need for new physics to explain its existence.

In a groundbreaking discovery, scientists have detected the most powerful cosmic ray in over three decades. This turbocharged particle from outer space has left researchers puzzled, as its exact origin remains a mystery. With an estimated energy of 240 exa-electronvolts (EeV), comparable to the record-breaking Oh-My-God particle discovered in 1991, scientists are now questioning what could produce such immense energy. The findings, published in Science, have sparked discussions about the need for new physics to explain this phenomenon.

The Nature of Cosmic Rays:

Contrary to their name, cosmic rays are not rays at all but high-energy subatomic particles, often protons, traveling through space at speeds close to that of light. Ultrahigh-energy cosmic rays surpass one EeV in energy, which is a million times greater than the levels reached by human-made particle accelerators. These cosmic rays are rarely observed, with fewer than one of these particles arriving on each square kilometer of Earth every century.

The Discovery:

Toshihiro Fujii, an astronomer at Osaka Metropolitan University in Japan, stumbled upon peculiar signals during a routine data check at the Telescope Array, a cosmic-ray detector in Utah. The signals indicated that the detectors had been impacted by an incredibly energetic particle. Initially skeptical, Fujii eventually confirmed that the measurements were consistent with ultrahigh-energy cosmic rays. The particle was affectionately named ‘Amaterasu’ after a Japanese Sun goddess.

The Mystery of Amaterasu:

Despite confirming the presence of Amaterasu, Fujii and his team were unable to determine its exact source. Typically, ultrahigh-energy cosmic rays travel through space smoothly, as they are less affected by magnetic fields compared to low-energy cosmic rays. This would have made it easier to identify the stellar explosion, black hole, or galaxy from which Amaterasu originated. However, calculations placed the source of the ray in a region with few galaxies, leaving researchers perplexed. Even after considering possible source galaxies and objects just outside the ray’s arrival direction, no suitable match was found.

Possible Explanations:

One explanation for the inability to pinpoint Amaterasu’s source could be inaccuracies in the models used to estimate how magnetic fields influence the path of cosmic rays. Clancy James, an astronomer at Curtin University, suggests that these models might require adjustment, potentially leading to a different direction for Amaterasu than initially calculated. Another possibility is that unknown physical processes enable ultrahigh-energy cosmic rays to travel much greater distances than previously believed. Jose Bellido Caceres, an astroparticle physicist at the University of Adelaide, suggests that this discovery could indicate the presence of new physics, providing an opportunity to explore particle interactions at extreme energies that cannot be replicated by Earth-based accelerators.

Future Research:

Fujii and his team are currently upgrading the Telescope Array to enhance its sensitivity fourfold. This upgrade will enable researchers to capture more of these rare ultrahigh-energy cosmic rays and trace their origins with greater precision. The hope is that these advancements will shed light on the mysterious source of Amaterasu and potentially uncover new insights into the nature of cosmic rays.


The recent detection of the most powerful cosmic ray in decades has left scientists intrigued and searching for answers. The enigmatic Amaterasu particle challenges our understanding of the universe and raises questions about the need for new physics to explain its existence. As researchers continue to upgrade their instruments and refine their models, they aim to unlock the secrets of ultrahigh-energy cosmic rays, offering a glimpse into the extreme energies and phenomena that exist beyond our planet.






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