In 1991, an experiment conducted by the University of Utah in the USA detected the most energetic cosmic ray ever observed, subsequently nicknamed the “Oh-My-God” particle. Since then, the mystery remains as to the origin of these ultra-energetic particles. Recently, a new particle was detected, raising new questions.
The discovery of the Amaterasu particle
On May 27, 2021, the experience of “Telescope Array” detected the second highest extreme energy cosmic ray, with an energy of 2.4 x 1020eV. This unique subatomic particle was named particule Amaterasu, after the sun goddess of Japanese mythology. The direction of arrival of this particle seems to come from Local Voidan empty area of space located at the edge of our galaxy, the Milky Way.
Natural particle accelerators
Cosmic rays are echoes of violent celestial events that stripped matter of its subatomic structures and hurled it across the universe at near the speed of light. Ultra-energetic cosmic rays must exceed 5 x 1019 eV, meaning a single subatomic particle carries the same kinetic energy as a fastball thrown by a professional baseball pitcher.
Artist’s illustration of ultra-high energy cosmic ray astronomy to clarify extremely energetic phenomena in contrast to a lower energy cosmic ray whose trajectory is distorted by electromagnetic fields. Credit: Osaka Metropolitan University/Kyoto University/Ryuunosuke Takeshige
Beyond the theoretical limit
Astrophysicists have calculated a theoretical limit, called limite de Greisen-Zatsepin-Kuzmin (GZK), as the maximum energy a proton can hold while traveling long distances before interactions with the cosmic microwave background radiation strip it of energy. The new Amaterasu particle, with an energy of 2.4 x 1020 eV, and the Oh-My-God particle, with an energy of 3.2 x 1020 eV, easily exceed this limit.
Animation reproducing the timing and intensity of secondary particles hitting the surface detectors of the telescope array.
The expansion of the Telescope Network
The telescope network is currently being expanded, with theaddition of 500 new scintillation detectors. Once complete, this expansion will allow sampling of cosmic ray-induced particle showers over an area of 2,900 km2 (1,100 mi2), an area almost the size of the state of Rhode Island. Researchers hope this expanded footprint will help capture more events and shed light on these mysterious phenomena.
Synthetic
The discovery of the particule Amaterasuas well as that of the particle Oh-My-God, raises many questions about the origin and nature of these ultra-energetic phenomena. Despite technological advances and the expansion of the telescope network, astrophysicists are still faced with a mystery. Research continues to try to understand these rare and enigmatic events which defy the theoretical limits of particle physics.
For a better understanding
1. What is the Oh-My-God particle?
The Oh-My-God particle is an ultra-energetic cosmic ray detected in 1991 by the University of Utah. It has extremely high energy, exceeding the theoretical limits of particle physics.
2. What is the Amaterasu particle?
The Amaterasu particle is an extreme energy cosmic ray detected in 2021 by the telescope network. It has an energy of 2.4 x 1020eV and appears to come from the Local Void, an empty area of space located at the edge of our galaxy.
3. What is the Greisen-Zatsepin-Kuzmin (GZK) limit?
The GZK limit is a theoretical limit calculated by astrophysicists, representing the maximum energy a proton can hold while traveling long distances before interactions with the cosmic microwave background radiation rob it of energy.
The Telescope Array is an array of surface detectors used to detect ultra-energetic cosmic rays. It is currently being expanded to cover an area of 2,900 km2 to capture more events and study these mysterious phenomena.
5. What are the hypotheses on the origin of these ultra-energetic particles?
Astrophysicists still face a mystery regarding the origin of these ultra-energetic particles. Hypotheses include defects in the structure of space-time or colliding cosmic strings, but no conventional explanation has yet been found.
Main lessons
TeachingDescriptionOh-My-God particleDetected in 1991, it has extremely high energy, exceeding the theoretical limits of particle physics.Amaterasu particleDetected in 2021, it has an energy of 2.4 x 10 to the power of 20 eV and appears to come from the local vacuum , an empty area of space located at the edge of our galaxy.GZK limitTheoretical limit calculated by astrophysicists, representing the maximum energy a proton can contain while traveling long distances before interactions with background radiation cosmic rays do not take away energy.Telescope arrayAn array of surface detectors used to detect ultra-energetic cosmic rays. It is currently being expanded to cover an area of 2,900 km2.Hypotheses about the originAstrophysicists still face a mystery regarding the origin of these ultra-energetic particles. Hypotheses include defects in the structure of space-time or colliding cosmic strings, but no conventional explanation has yet been found.Composition of cosmic raysResearchers analyze the composition of cosmic rays for clues on their origin. The Amaterasu particle is probably a proton.Particle trajectoryUltra-energetic particles like the Oh-My-God and Amaterasu particles pass through intergalactic space relatively without deviation.Powerful celestial eventsOnly the most powerful celestial events can produce ultra-energetic particles such as the Oh-My-God and Amaterasu particles.Particle EnergyUltra-energetic particles have energies so high that they exceed the kinetic energy of a fastball thrown by a professional baseball pitcher.Network ExpansionThe Telescope Network is being expanded to cover an area of 2,900 km2, which should make it possible to capture more events and elucidate the mystery of these ultra-energetic particles.
References
Main illustration caption: Artist’s illustration of the extremely energetic cosmic ray observed by an array of surface detectors in the Telescope Array experiment, called the “Amaterasu particle”. Credit: Osaka Metropolitan University/L-INSIGHT, Kyoto University/Ryuunosuke Takeshige
[ Rédaction ]
2023-11-24 18:36:52
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