1991 жылғы аса жоғары энергиялы ғарыш сәулесі

Ultra high energy cosmic ray detected in 1991

The Oh My God particle was an ultra high energy cosmic ray detected on 15 October 1991 by the Fly's Eye camera in Dugway Proving Ground, Utah, United States. Its energy was estimated as 3.2 (320 exa eV). The particle's energy was unexpected and called into question prevailing theories about the origin and propagation of cosmic rays.

It is not known what kind of particle it was, but most cosmic rays are protons. If is the rest mass of the particle and is its kinetic energy (energy above the rest mass energy), then its speed was times the speed of light. Assuming it was a proton, for which is 938 MeV, this means it was traveling at 0.9999999999999999999999951 times the speed of light, its Lorentz factor was 3.2 and its rapidity was 27.1. Due to special relativity, the relativistic time dilation experienced by a proton traveling at this speed would be extreme. If the proton originated from a distance of 1.5 billion light years, it would take approximately 1.71 days in the reference frame of the proton to travel that distance.

The Oh My God particles energy was estimated as 3.2, or 51. Although this amount is phenomenally large for a single elementary particle – far outstripping the highest energy that human technology can generate in a particle – it is still far below the level of the Planck scale, where exotic physics is expected. The energy released by this extremely small particle is comparable to dropping a 1 kg mass from an height of 5.2 (similar to the roof height of a medium sized two story building) on Earth. So, a sub atomic particle with as much energy as the kinetic or potential energy of a macroscopic object in ordinary conditions.

The Oh My God particle had (100 quintillion) times the photon energy of visible light, equivalent to a baseball travelling at about Its energy was 20 million times greater than the highest photon energy measured in electromagnetic radiation emitted by an extragalactic object, the blazar Markarian 501.

While the particle's energy was higher than anything achieved in terrestrial accelerators, it was still about 40 million times lower than the Planck energy (1.2208901). Particles of that energy would be required in order to expose effects on the Planck scale. A proton with that much energy would travel 1.665 times closer to the speed of light than the Oh My God particle did. As viewed from Earth and observed in Earth's reference frame, it would take about 3.579 (2.59 times the current age of the universe) for a photon to overtake a Planck energy proton with a 1 cm lead.

Since the first observation, hundreds of similar events (energy 5.7 or greater) have been recorded, confirming the phenomenon. These ultra high energy cosmic ray particles are very rare; the energy of most cosmic ray particles is between  eV and  eV. More recent studies using the Telescope Array Project have suggested a source of the particles within a 20 degree radius "warm spot" in the direction of the constellation Ursa Major. The Amaterasu particle, named after the sun goddess in Japanese mythology, was detected in 2021 and later identified in 2023, using the Telescope Array observatory in Utah, United States. It had an energy exceeding 240 exa electron volts (2.4 eV). This particle appears to have emerged from the Local Void, an empty area of space bordering the Milky Way galaxy. It contained an amount of energy comparable to dropping a brick from the height of the waist. No promising astronomical object matching the direction from which the cosmic ray arrived has been identified.