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Japanese scientist Toshihiro Fujii made a groundbreaking discovery in the realm of cosmic rays, unveiling an ultra-high-energy event that would be named 'Amaterasu.' This cosmic ray, observed between May 2008 and November 2021 by the Telescope Array Project in the U.S., has sparked immense interest in the scientific community due to its extraordinary energy levels, reaching 240 exa-electron-volts (EeV), making it the second-highest-energy cosmic ray ever discovered.

Understanding Cosmic Rays:

Cosmic rays are energetic particles originating from outer space and the sun.

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.

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.

Typically consisting of protons and alpha particles, they provide a window into the mysteries of the universe. While low-intensity cosmic rays reach Earth's surface, their higher-energy counterparts often collide with atmospheric gases, producing cascades of particles.

Despite being discovered over 86 years ago, the sources and reasons behind the extreme energy of cosmic rays remain elusive.

The Amaterasu Cosmic Ray's Energy:

The data collected by the Telescope Array Project revealed that Amaterasu possesses an energy level of 240 EeV, a staggering 40 million times higher than the energy produced by the Large Hadron Collider (LHC), the most powerful particle accelerator on Earth. 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.

This unprecedented energy level opens up new possibilities for scientific exploration and challenges existing models within the Standard Model of particle physics.

Ultra-High-Energy Cosmic Rays (UHECRs):

Amaterasu falls into the category of ultra-high-energy cosmic rays (UHECRs), subatomic particles with energies surpassing 1 EeV. While scientists have observed UHECRs exceeding 100 EeV, those with energies beyond 60 EeV face challenges in surviving due to the cosmic microwave background (CMB). This radiation, a remnant of the Big Bang, suppresses the flux of UHECRs, limiting their observable distance to approximately 50-100 megaparsecs.

Journey of a Cosmic Ray:

The journey of a UHECR through the vast expanse of space, traveling near the speed of light, spans millions of years. This longevity is crucial for scientists as it allows the observation of cosmic rays that have traversed distances where suppression by the CMB has not been complete.

Amaterasu's Mysterious Origin:

One of the most intriguing aspects of the Amaterasu cosmic ray is its apparent origin from an empty part of the universe. Despite its unparalleled energy, when astronomers trace its direction, there is nothing observable. This enigma challenges existing astronomical knowledge, prompting scientists to consider possibilities beyond the Standard Model.

Proposed Explanations for Amaterasu's Origin:

Dr. Fujii and his colleagues put forward three potential explanations for Amaterasu's origin. It could be from an unidentified source, have interacted with a stronger-than-expected magnetic field, altering its trajectory, or necessitate a reevaluation of high-energy particle physics.

Comparisons to Previous Discoveries:

In 1991, another high-energy cosmic ray with an even greater energy of 320 EeV, known as the "Oh My God" particle, was detected at the Dugway Proving Ground in Utah. While remaining the most energetic cosmic ray ever recorded, its discovery adds to these cosmic anomalies' fascination.

Solar Cosmic Rays vs. Galactic Cosmic Rays:

Cosmic rays can be classified into galactic cosmic rays (GCR) originating from beyond the solar system and solar cosmic rays, primarily protons emitted by the sun during solar flares. The study of these cosmic rays provides insights into the mass ratio of helium to hydrogen nuclei, resembling the abundance of elements in the early universe.

Impact on Earth's Atmosphere:

As GCRs constantly bombard Earth, their interaction with the atmosphere, specifically ionizing air molecules, occurs at altitudes of about 3 km and above. This interaction alters the energy levels of cosmic ray particles, highlighting the significance of their energy in shaping our understanding of high-energy physics.

Unveiling New Theories:

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

The discovery of Amaterasu's unprecedented energy levels holds the potential to revolutionize our understanding of the universe's subatomic building blocks. The absence of a clear astronomical source challenges physicists to explore new theories and concepts that extend beyond the boundaries of the Standard Model.

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.

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.

Conclusion:

The Amaterasu cosmic ray stands as a testament to the ongoing mysteries within the universe. Its unparalleled energy levels, mysterious origin, and apparent divergence from known astronomical phenomena provide a unique opportunity for scientists to delve deeper into the fundamental principles of particle physics. As researchers continue to analyze cosmic rays and their implications, the quest for understanding the cosmos at its most fundamental levels takes an exciting leap forward. The enigma of Amaterasu beckons us to unlock the secrets hidden within the vast cosmic tapestry, pushing the boundaries of our current scientific knowledge.

Source- The Hindu