Science and Technology Daily reporter Jin Feng
More than 100 years ago, humans discovered a class of high-energy particles from outer space -cosmic rays, which dominate the formation of elements such as beryllium and boron, and can also produce carbon 14 Wait for unstable nucleus. However, the origin of cosmic rays can be called the mystery of the century.
On April 2, the reporter learned from the Purple Mountain Observatory of the Chinese Academy of Sciences that the researcher Liu Siming's team published a study in the internationally renowned journal "ASTROPHYSICAL JOURNAL", revealing a possibility. They discovered for the first time in the world that the supernova remnant can accelerate the cosmic ray to one trillion electron volts (100 TeV) at most.
"This is in contradiction with the traditional belief that supernova remnants can accelerate cosmic rays to peta billion electron volts (PeV). This indicates that there is also a type of ultra-high energy cosmic ray source that can accelerate cosmic rays to More than one trillion electron volts. But where the latter comes from, we still need to study." said Liu Siming, the corresponding author of this article.
The distribution of gamma-ray supernova remnants in the Milky Way. Photo courtesy Liu Siming
Cosmic rays can produce a large number of secondary high-energy particles in the atmosphere. These particles can subtly affect the evolution of species by generating a certain radiation dose in the organism.
"The energy of cosmic ray particles is very high, and they are produced in the explosion process of celestial bodies. The remnants of supernova explosion are considered to be the most important source of cosmic rays in the Milky Way." Liu Siming said, based on the flow of cosmic rays. The energy spectrum feature that varies with energy. It is generally believed that cosmic rays below petavolts come from the explosion process of the Milky Way, while cosmic rays above tens of billions of electron volts mainly come from the absorption of supermassive black holes. Product process.
He introduced,Observation and analysis in the past ten years have shown that cosmic rays from billions of electron volts to trillions of electron volts may mainly come from the remnants of supernovae that evolved in an environment with relatively high gas density. The gamma-ray flux of these relics decreases rapidly with the increase of energy, and most of the gamma-rays are radiated in the energy range of hundreds of millions of electron volts. On the other hand, the gamma-ray flux of supernova remnants that evolve in an environment with relatively low gas density will decrease slowly with the increase of energy. This is often called a hard spectrum, and can accelerate the cosmic rays to several points. Ten trillion electron volts.
However, with the latest discovery of the research team, this phenomenon will have more possibilities. "We collected multi-band observation data of nearly 40 gamma-ray supernova remnants from 1000 light-years to 50,000 light-years from the earth, and analyzed more than a dozen gamma-rays that evolved in a low gas density environment. Supernova relics, it turns out that these relics can accelerate cosmic rays to about one trillion electron volts at most, which means that the ultra-high-energy cosmic rays above 100 TeV come from another type of cosmic ray source." Liu Siming said. The
study also marked the distribution of known gamma-ray supernova remnants in the Milky Way. They found that the remnants of hard-spectrum gamma-ray supernovae are mainly distributed near solar system , and their gamma-ray luminosity is generally low. The remnants of bright gamma-ray supernovae are far from the solar system.
Editor: Zhang Qiqi
Review: Julie
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