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"Sun goddess" cosmic ray strikes Earth, leaving scientists baffled

A recent scientific discovery could be straight out of a science fiction novel. Researchers involved in the Telescope Array experiment have identified an extraordinarily energetic cosmic ray. This particle, named “Amaterasu,” originated from outside our galaxy and boasts an energy level of approximately 240 exa-electron volts (EeV).

Despite its remarkable detection, the analysis reveals that the direction from which this cosmic ray arrived does not align with any discernible source.

Cosmic rays are not just particles from space; they are energetic charged particles that come from both galactic and extragalactic sources. Among these, the extremely high-energy cosmic rays are particularly rare and fascinating.

These rays can possess energy levels greater than 10^18 electron volts (EeV), a figure that is about a million times higher than the energy achievable by the most powerful human-made accelerators.

The Telescope Array experiment

Associate Professor Toshihiro Fujii is from the Graduate School of Science and Nambu Yoichiro Institute of Theoretical and Experimental Physics at Osaka Metropolitan University. Since 2008, Professor Fujii, alongside an international team, has been at the forefront of the Telescope Array experiment.

This experiment involves a cosmic ray detector comprising 507 scintillator surface stations spread over an area of 700 square kilometers in Utah, United States. On May 27, 2021, this team made a groundbreaking discovery: they detected a particle with an energy level of 244 EeV.

“When I first discovered this ultra-high-energy cosmic ray, I thought there must have been a mistake, as it showed an energy level unprecedented in the last 3 decades,” Professor Fujii remarked.

The Amaterasu particle

This newly detected particle has been named “Amaterasu,” after the sun goddess in Shinto religion, who is believed to have played a crucial role in the creation of Japan.

The Amaterasu particle’s energy level is comparable to the “Oh-My-God” particle, which held the record for the most energetic cosmic ray with an estimated energy of 320 EeV when detected in 1991.

Significance of the Amaterasu particle

The discovery of the Amaterasu particle raises numerous questions: What is its origin? What type of particle is it? Unfortunately, these questions remain unanswered.

As mentioned previously, no astronomical object corresponding to the direction from which the cosmic ray originated has been identified. This suggests the possibility of unknown astronomical phenomena or novel physical origins that extend beyond the current Standard Model of particle physics.

Ongoing research

Professor Fujii and his team are committed to continuing their research with the Telescope Array experiment. They are also involved in an upgraded experiment, known as TAx4, which promises four times the sensitivity of the current setup. Along with next-generation observatories, these advancements will aid in a more detailed investigation into the source of this extremely energetic particle.

In summary, the Amaterasu particle not only challenges our understanding of cosmic rays but also opens the door to potentially revolutionary discoveries in astrophysics and particle physics. As researchers continue to unravel the mysteries of these high-energy particles, we may be on the verge of uncovering new aspects of our universe, far beyond what we currently comprehend.

More about cosmic rays

As discussed above, cosmic rays are high-energy particles that originate from outer space and travel at nearly the speed of light. They consist primarily of protons, atomic nuclei, and a small fraction of heavier elements, including electrons and positrons. These particles carry immense energy, often exceeding energies found in even the most powerful particle accelerators on Earth.

Origins and composition

Cosmic rays originate from various sources in the universe, including the sun, distant stars, supernova explosions, and possibly even distant galaxies. The majority are atomic nuclei stripped of their electron shells, with protons (hydrogen nuclei) being the most common. Helium nuclei (alpha particles) and heavier nuclei like carbon, oxygen, and iron also constitute a significant portion.

Interaction with Earth’s atmosphere

Upon entering Earth’s atmosphere, cosmic rays collide with atomic nuclei in the air, creating showers of secondary particles, including mesons, electrons, and photons. These secondary particles can sometimes be detected on the Earth’s surface, providing valuable information about the primary cosmic rays.

Scientific significance of cosmic rays

Cosmic rays are of great scientific interest for several reasons. They provide insights into high-energy physics, astrophysics, and cosmology. Studying cosmic rays helps scientists understand the fundamental forces and particles in the universe, the behavior of stars, and the interstellar medium. Additionally, cosmic rays are a key factor in the atmospheric chemistry of Earth and other planets.

Potential hazards

Cosmic rays pose potential hazards to astronauts in space and high-altitude flights, as they can penetrate spacecraft and aircraft. Prolonged exposure to cosmic rays can lead to increased risks of cancer and other health issues. Understanding and mitigating these risks is crucial for future space exploration and aviation safety.

Cosmic rays are not only a fascinating subject of scientific study but also have practical implications for space travel and understanding the universe’s fundamental properties.

More about the “Oh-my-God” particle

In the world of astrophysics, few discoveries stir as much excitement as the detection of extremely high-energy cosmic rays. Among these, the “Oh-My-God” particle, as mentioned above, stands out for its almost unimaginable energy levels.

Background on cosmic rays

Cosmic rays are high-energy particles that travel through space, striking the Earth from all directions. Most originate from the sun or from outside our solar system, possibly even from distant galaxies. They consist primarily of protons or atomic nuclei, and their energy levels can vary widely.


The “Oh-My-God” particle, named for its shockingly high energy, was first detected on the night of October 15, 1991. Researchers using the University of Utah’s Fly’s Eye Cosmic Ray Detector spotted this particle. Its energy was estimated to be around 320 exa-electron volts (EeV) – more than 50 million times greater than the highest energy achieved in any human-made particle accelerator at the time.


This particle’s energy posed a significant challenge to scientists. It seemed to violate the so-called Greisen–Zatsepin–Kuzmin (GZK) limit, a theoretical upper limit on the energy of cosmic rays from distant sources.

This limit is based on interactions between cosmic rays and the cosmic microwave background radiation, which should theoretically sap these particles of their energy over long distances. The detection of the “Oh-My-God” particle suggested either a violation of this limit or indicated that it originated from a relatively close source in cosmic terms.


The discovery spurred intense research and debate within the astrophysics community. It raised questions about the sources of such high-energy particles and the mechanisms that could accelerate them to such extreme velocities. Understanding these processes is crucial for our broader comprehension of the universe, including the nature of galaxies, quasars, and black holes.

In summary, the “Oh-My-God” particle remains one of the most extreme examples of cosmic rays ever observed. Its detection has played a pivotal role in advancing our understanding of the universe, challenging existing theories, and pushing the boundaries of astrophysics.

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