2021-10-25

Solve the Centennial mystery of the source of high-energy cosmic rays: supernova debris is the answer

By yqqlm yqqlm

Visit: Alibaba cloud 11.11 shangyun Carnival activity hall 2021 tmall double 11 red envelope Jingdong double 11 “top Beijing Post” collection entrance

abd2c1a5233031e - Solve the Centennial mystery of the source of high-energy cosmic rays: supernova debris is the answer

when high-energy cosmic rays hit the top of the earth’s atmosphere, high-energy particle “showers” will occur. Cosmic rays were accidentally discovered in 1912

this includes the origin of cosmic rays and how the main component of cosmic rays (protons) was accelerated to such a high speed. In a new study at Nagoya University in Japan, astronomers have quantified the amount of cosmic rays produced in supernova remnants for the first time. This research has helped solve a mystery that has lasted for a hundred years and is an important step in accurately determining the source of cosmic rays

although astronomers theoretically believe that cosmic rays come from many sources, including the sun, supernovae, gamma ray bursts and active galactic nuclei (quasars), their exact origin has been a mystery since they were first discovered in 1912. Another hypothesis put forward by astronomers is that supernova debris (the aftermath of supernova explosion) is the reason why cosmic ray particles accelerate to close to the speed of light

Solve the Centennial mystery of the source of high-energy cosmic rays: supernova debris is the answer

schematic diagram of cosmic ray proton interaction and electron photon interaction to produce gamma rays respectively. Cosmic ray protons interact with interstellar protons (such as molecules and hydrogen atoms) to produce neutral mesons, which then decay rapidly into two gamma ray photons (hadron process). Cosmic ray electrons excite interstellar photons (mainly cosmic microwave background radiation) through anti Compton scattering (lepton process) and convert them into gamma ray energy

when cosmic rays pass through the Milky way, they play an important role in the chemical evolution of interstellar media. Therefore, understanding the origin of cosmic rays is very important to understand how galaxies evolve. In recent years, with the improvement of observation technology, some scientists use the latest observation results to speculate that supernova debris can produce cosmic rays because their accelerated protons interact with protons in interstellar media to produce very high energy (VHE) gamma rays

however, gamma rays can also be generated by the interaction between electrons and photons in the interstellar medium, which can be in the form of infrared photons or cosmic microwave background (CMB). Therefore, determining which of these two sources accounts for a larger proportion is very important to determine the source of cosmic rays. To clarify this point, researchers from Nagoya University, the National Astronomical Observatory of Japan (NAOJ) and the University of Adelaide in Australia observed the supernova remnant Rx j1713.7 3946 (Rx J1713)

the key to this study is the new method developed by researchers to quantify interstellar space gamma ray sources. Past observations have shown that in the interstellar medium, the intensity of very high energy gamma rays produced by the collision of protons with other protons is directly proportional to the density of interstellar gas, which can be identified by wireless wire imaging. On the other hand, gamma rays generated by the interaction between electrons and photons in interstellar media are also considered to be directly proportional to the intensity of non thermal X-rays from electrons

Solve the Centennial mystery of the source of high-energy cosmic rays: supernova debris is the answer(1)

in order to carry out the research, the research team used the data obtained by the high-energy stereo vision telescope system (Hess). Hess, located in Namibia, is a very high energy gamma ray observatory (operated by the Max Planck Institute of Nuclear Physics). They then combined these data with X-ray data obtained by the European Space Agency’s X-ray multi mirror mission (XMM Newton satellite) and relevant data on gas distribution in interstellar media

through comprehensive analysis of these three data sets, researchers determined that protons accounted for 67 ± 8% of cosmic rays and electrons accounted for 33 ± 8% – about 7:3. These findings are groundbreaking because it is the first time to quantify the possible origin of cosmic rays and the clearest evidence to date that supernova debris is the source of cosmic rays

these results also show that gamma rays generated by protons are more common in gas rich interstellar regions, while gamma rays generated by electrons are more intense in gas poor regions. This supports the prediction of many researchers that these two mechanisms jointly affect the evolution of interstellar media

Yasuo Fukui, the principal author and emeritus professor of the study, said: “without international cooperation, this new method cannot be realized. This will be applied to the study of more supernova remnants. In addition to the existing observation stations, the launch of the next generation gamma ray telescope CTA (Cherenkov telescope array) will also greatly promote the study of the origin of cosmic rays.”

at the same time, Dr. Hidetoshi Sano, co-author of the National Astronomical Observatory of Japan, led the analysis of the data set of the European Space Agency’s X-ray multi mirror mission archive. From this perspective, this study shows how international cooperation and data sharing make various cutting-edge research possible. With the improvement of observation instruments, the optimization of methods and the increase of cooperation opportunities, mankind is entering a new era in which astronomical breakthroughs have become the norm. (Ren Tian)