Astronomers shocked by mysterious ultra-high-energy cosmic ray – “What’s going on?”

Astrophysicists at the University of Utah and the telescope array have detected cosmic rays with energies beyond theoretical limits, challenging current understanding of particle physics. These discoveries, including the Oh-My-God and Amaterasu particles, point to unknown cosmic phenomena and are the focus of ongoing research.

Next to the Oh-My-God particle, the newly named Amaterasu particle deepens the mystery of the origin, propagation, and particle physics of rare, ultra-high-energy cosmic rays.

In 1991, the University of Utah’s University of Utah eye experiment detected the highest-energy cosmic rays ever observed. Later called the oh-my-god particle, the energy of the cosmic rays shocked astrophysicists. Nothing in our galaxy has the energy to produce it, and the particle had more energy than is theoretically possible for cosmic rays traveling to Earth from other galaxies. Simply put, there should be no particle.

Mysteries of Astronomy

The telescope array has observed more than 30 ultra-high-energy cosmic rays, though none have approached oh-my-god-level energies. No observations have yet revealed their origin or how they could travel to Earth.

The Amethyst particle hit Earth's atmosphere

Artist’s rendering of a highly energetic cosmic ray observed by the Surface Detection Array of the Telescope Array Experiment, dubbed the “Amaterasu particle.” Credit: Osaka Metropolitan University/L-Inside, Kyoto University/Ryunosuke Takeshige

On May 27, 2021, the Telescope Array experiment detected the second highest intensity cosmic ray. 2.4 x 10 in20eV, the energy of this single subatomic particle is equivalent to dropping a brick on your toe from waist height. Led by the University of Utah (U) and the University of Tokyo, the telescope array consists of 507 surface detection stations covering a 700 km square grid.2 (~270 miles2Utah in the desert west of the state, outside the Delta. The event triggered 23 detectors in the northwest part of the telescope array, 48 km away.2 (18.5 mi2) whose direction of arrival originates from the local void, the empty region at the boundary of space milky way Galaxy.

“The particles are so energetic that they shouldn’t be affected by galactic and extrastellar magnetic fields. You can pinpoint where they’re coming from in the sky,” said John Matthews, the U’s telescope array co-spokesman and co-author of the study. “But the oh-my-god particle and this new In the case of the particle, you trace its path back to its source, and there is no energy high enough to create it. That’s the mystery—what’s going on?”

Amaterasu particle

In their observation published in the journal on November 24, 2023 Science, an international collaboration of researchers described the ultra-high-energy cosmic ray, evaluated its characteristics, and concluded that it is a rare phenomenon that follows particle physics unknown to science. The researchers named it the Amaterasu particle after the sun goddess in Japanese mythology. The Oh-My-God and Amaterasu particles were detected using different observational techniques, confirming that although rare, these ultra-high-energy events are real.

Ultra-High-Energy Cosmic Ray Astronomy

Astronomer’s illustration of an ultra-high-energy cosmic ray to elucidate more energetic phenomena as opposed to a weaker cosmic ray struck by electromagnetic fields. Credit: Osaka Metropolitan University/Kyoto University/Ryunosuke Takeshige

“These events seem to be coming from completely different places in the sky. It’s not like there’s a mysterious source,” said John Bells, a professor at the U and co-author of the study. “It could be flaws in the structure of spacetime, colliding cosmic strings.” I mean, I spit out the crazy ideas people come up with for lack of a conventional explanation.

Nature’s particle accelerators

Cosmic rays are echoes of violent celestial events that strip matter down to its subatomic structures and blast through the universe at nearly the speed of light. Basically cosmic rays are charged particles with a wide range of energies consisting of positive protons, negative electrons or entire nuclei that travel through space and rain down on Earth continuously.

Cosmic rays strike the Earth’s upper atmosphere and tear apart the nuclei of oxygen and nitrogen gas, creating many secondary particles. These travel some distance into the atmosphere and repeat the process, creating a shower of billions of secondary particles that scatter on the surface. The footprint of this secondary shower is huge and requires detectors to cover an area as large as a telescope array. Surface detectors use a suite of instruments that provide researchers with information about each cosmic ray; The timing of the signal shows its path and the amount of charged particles hitting each detector reveals the energy of the primary particle.

Because the particles have an electric charge, their flight path resembles a ball in a pinball machine as they zigzag against the electromagnetic fields in the cosmic microwave background. It is almost impossible to trace the path of most cosmic rays, which are at the low to medium end of the energy spectrum. Even high-energy cosmic rays are distorted by the microwave background. Particles with Oh-My-God and Amaterasu energy are relatively unbent in intergalactic space. Only the most powerful of celestial phenomena can produce them.

“Things that people think are energetic, like a supernova, are not energetic enough for this. You need a lot of energy, really a lot of magnetic fields, to control the particle as it accelerates,” Matthews said.

The mystery of ultra-high-energy cosmic rays

Ultra-high-energy cosmic rays must be greater than 5 x 1019 E.V. This means that a subatomic particle has the same kinetic energy as a major league pitcher’s fastball and millions of times more energy than any man-made particle accelerator can achieve. Astrophysicists have calculated this theoretical limit, known as the Griesen-Satzepin-Kuzmin (GZK) cut, because it is the maximum energy at which a proton can travel the longest distance before the interactions of the microwave background radiation gain their energy. Known source candidates, such as active galactic nuclei or black holes with accretion disks emitting particle jets, are 160 million light-years away from Earth. The new particle is 2.4 x 1020 eV and 3.2 x 10 O-my-god particle20 eV easily exceeds the cutoff.

Researchers examine cosmic ray composition for clues to its origin. A heavier particle, such as iron nuclei, is heavier, more charged, and more able to bend in a magnetic field than lighter particles made of protons from hydrogen. Atom. The new particle may be a proton. A cosmic ray with energies beyond the GZK cut of particle physics, the microwave background is powerful enough to distort its path, but its path points back toward empty space.

“Perhaps the magnetic fields are stronger than we thought, but this does not agree with other observations that show they are not strong enough to produce significant bending at these ten to twentieth electron volt energies,” Bells said. “It’s a real mystery.”

Research and expand the telescope array

The Telescopic array It is uniquely positioned to detect ultra-high-energy cosmic rays. It is at about 1,200 m (4,000 ft), the height sweet-spot where secondary particles allow maximum growth, but before they begin to decay. Its location in Utah’s western desert provides ideal atmospheric conditions in two ways: dry air is important because moisture absorbs the ultraviolet light needed for detection; And the region’s dark skies are necessary because light pollution creates too much noise and obscures cosmic rays.

Astrophysicists are still puzzled by the mysterious phenomena. The telescope array is in the middle of an expansion that they hope will help crack the case. When completed, 500 new scintillator detectors will expand the telescope array to detect cosmic ray-induced particle showers 2,900 km away.2 (1,100 mi2 ), almost the size of Rhode Island. A larger footprint captures more events that shed light on what’s going on.

Learn more about this discovery:

Reference: “Most energetic cosmic ray observed by surface detection array” 23 Nov 2023, Science.
DOI: 10.1126/science.abo5095

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