The second newly named Amaterasu particle after the Oh My God particle deepens the mysteries of the origin, propagation, and particle physics of rare ultrahigh-energy cosmic rays.
In 1991, the University of Utah’s Fly’s Eye experiment detected the most energetic cosmic rays ever observed. The energy of this cosmic ray, later called the Oh My God Particle, shocked astrophysicists. There was nothing in our galaxy with the power to produce it, and the particles had more energy than cosmic rays traveling to Earth from other galaxies are theoretically possible. Simply put, particles should not exist.
astronomical mysteries
Since then, the telescope array has observed more than 30 extremely high-energy cosmic rays, but none reached Oh My God levels of energy. There are no observations yet that reveal their origin or how they are able to travel to Earth.
On May 27, 2021, the Telescope Array experiment detected the second highest extreme energy cosmic ray. For 2.4×1020eV, the energy of this single subatomic particle is equivalent to dropping a brick from waist height onto your toes. The telescope array, led by the University of Utah and the University of Tokyo, consists of 507 surface detection stations arranged in a square grid covering 700 km.2 (about 270 miles2) A suburb of Delta in Utah’s Western Desert. The event activated 23 detectors in the northwestern region of the Telescope array, sending droplets over a distance of 48 kilometers.2 (29.5 miles2). Its direction of arrival appeared to be from the local void, the empty space adjacent to Earth. milky way Galaxy.
“The particles are so high-energy that they shouldn’t be affected by galactic and extragalactic magnetic fields. We should be able to show where in the sky they came from,” said U.S. Telescope Array co-spokesman. said John Matthews, co-author of the study. “But in the case of the Oh My God particle and this new particle, even if we trace its trajectory back to its source, there’s nothing high enough energy to produce it. That’s the mystery of this case – what the heck? Is that happening?”
amaterasu particles
In their observations, published in the journal Nov. 24, 2023, science, an international collaboration of researchers described ultra-high-energy cosmic rays and evaluated their properties, concluding that the unusual phenomenon may follow particle physics unknown to science. The researchers named this particle the “Amaterasu particle,” after the sun goddess who appears in Japanese mythology. The Oh My God and Amaterasu particles were detected using a variety of observational techniques, confirming that, although rare, these ultra-high-energy events are real.
“These events appear to be coming from completely different parts of the sky. There’s no single mysterious source,” said study co-author John Beltz, a professor at the University of California. said. “It could be that there’s a flaw in the fabric of space-time and the cosmic strings are colliding. So I’m just spewing out crazy ideas that people come up with because there’s no conventional explanation.” ”
natural particle accelerator
Cosmic rays are echoes of violent astronomical events that strip matter down to its subatomic structure and fling it into space at nearly the speed of light. Essentially, cosmic rays are charged particles with a wide range of energies, consisting of positive protons, negative electrons, or entire atomic nuclei, that travel through space and almost constantly rain down on Earth.
Cosmic rays hit Earth’s upper atmosphere, detonating nuclei of oxygen and nitrogen gases and producing many secondary particles. These travel short distances through the atmosphere and repeat the process, forming showers of billions of secondary particles that scatter onto surfaces. The footprint of this secondary shower is enormous, requiring the detector to cover an area as large as a telescoping array. Surface detectors utilize a series of instruments that provide researchers with information about each cosmic ray. The timing of the signal indicates its trajectory, and the amount of charged particles hitting each detector reveals the energy of the primary particles.
Because particles have an electrical charge, their flight path resembles a ball in a pinball machine as it zigzags through the cosmic microwave background against an electromagnetic field. Tracing the trajectories of most cosmic rays at the lower to middle end of the energy spectrum is nearly impossible. Even high-energy cosmic rays are distorted by the microwave background. Particles with the energy of Oh My God and Amaterasu blow through intergalactic space relatively unbending. Only the most powerful celestial events can produce them.
“What people think of as energetic, like a supernova, is nowhere near enough energy for this. It takes a huge amount of energy and a very high magnetic field to confine the particles while they accelerate,” Matthews said. said.
The mystery of ultra-high energy cosmic rays
Ultra-high energy cosmic rays need to exceed 5×1019 eV. This means that a single subatomic particle carries the same kinetic energy as a major league pitcher’s fastball, and has tens of millions of times more energy than a man-made particle accelerator can achieve. Astrophysicists believe this theoretical limit, known as the Greisen-Zatsepin-Kuzmin (GZK) cutoff, can be maintained by protons traveling long distances before they lose energy due to the interaction effects of the microwave background radiation. Calculated as maximum energy. Known candidate sources, such as active galactic nuclei and black holes with accretion disks that emit particle jets, tend to be more than 160 million light-years from Earth. 2.4 x 10 new particles20 eV and 3.2 x 10 of Oh-My-God particles20 eV easily exceeds the cutoff.
Researchers are also analyzing the composition of cosmic rays for clues to their origins. A heavy particle, such as the nucleus of an iron atom, is heavier, has more charge, and bends more easily in a magnetic field than a lighter particle consisting of a proton from hydrogen. atom. The new particle is likely a proton. Particle physics suggests that cosmic rays with energies above the GZK cutoff are too strong for the microwave background to distort their path, but their trajectory heads into empty space.
“Magnetic fields may be stronger than we think, but that’s because other observations show that magnetic fields are not strong enough to produce significant curvature at energies of these 10 to 20 electron volts. It doesn’t match,” Beltz said. “It’s really a mystery.”
Research and expansion of telescope arrays
of telescope array It is uniquely positioned to detect ultra-high energy cosmic rays. It is located at about 1,200 meters (4,000 feet), an elevation sweet spot that allows for maximum development before secondary particles begin to decay. Located in Utah’s Western Desert, this location offers ideal atmospheric conditions in two ways. Dry air is important because moisture absorbs the ultraviolet light needed for detection. Dark skies in the region are also essential, as light pollution creates excessive noise and obscures cosmic rays.
Astrophysicists are still baffled by this mysterious phenomenon. The telescope array is in the midst of expansion in hopes of helping solve cases. Once completed, it will be expanded with 500 new scintillator detectors and a telescopic array that will sample cosmic ray-induced particle showers spanning 2,900 km.2 (1,100 miles2 ), its area is approximately the same as the state of Rhode Island. With a larger footprint, we hope to capture more events that reveal what’s going on.
For more information on this discovery, see:
Reference: “Very high-energy cosmic rays observed by surface detector array” November 23, 2023 science.
DOI: 10.1126/science.abo5095