Scientists are close to solving the century-old mystery of cosmic rays.
Scientists at the University of Nagoya in Japan have uncovered a century-old mystery of the origin of mysterious radiation in Earth’s upper atmosphere. They believe that supernova remnants are responsible for cosmic rays and their acceleration through space.
Everything you need to know about cosmic rays and their possible origins
Previous assumptions
In the past, scientists assumed that cosmic events were associated with the Sun, supernovae, gamma-ray bursts, and active galactic nuclei in quasars. However, their exact origin remained unconfirmed for more than 100 years.
Initial discovery
Astronomers first discovered cosmic rays in 1912. Scientists realized that the atmospheric radiation of our planet has distant origins. Since then, observations have found out incredible details about cosmic rays but several questions remained unanswered.
Importance of cosmic rays
Cosmic rays are extremely important for science. As they accelerate through space, they influence the chemical evolution of the interstellar medium, and thus, understanding them will help astronomers understand the evolution of galaxies and space in general.
Acceleration
Besides their origin, scientists have been theorizing about what exactly accelerates the protons in the cosmic rays to nearly the speed of light. In their new research, scientists were able to calculate the production of cosmic rays in a supernova remnant, which led to the long-awaited answer to the mystery.
Origins of gamma-rays
Over the past few years, observations have led to the theories that protons accelerated by supernovae interact with protons in the interstellar medium to produce very-high-energy gamma rays. However, gamma rays are also produced by electrons, which interact with infrared or microwave background photons. In order to confirm their theories, scientists have to determine the exact origin of cosmic rays.
Data
During their study, scientists combined gamma-ray and X-ray data from several telescopes and instruments around the world. What they found was that roughly 70% of cosmic rays are made from protons while electrons account for the remaining 30%.
Supernova remnants
To date, these results are the most convincing evidence that this phenomenon originates from supernova remnants. This is also the first time in history that scientists quantify their possible origins.
The density of the interstellar gas
Scientists based their results on the fact that the intensity of gamma rays caused by collisions of protons with other protons in the interstellar medium must be proportional to the density of the interstellar gas.
The intensity of nonthermal X-ray radiation
At the same time, the intensity of gamma radiation caused by collisions of photons with electrons should be proportional to the intensity of nonthermal X-ray radiation of electrons.
Gamma radiation
Thus, gamma radiation from protons is more common in gas-rich interstellar regions, while radiation caused by electrons is amplified in gas-poor regions. These results should aid scientists in their future studies on the evolution of the interstellar medium.
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Sources:
• Fukui, Y. (n.d.). Pursuing the Origin of the Gamma Rays in RX J1713.7-3946 Quantifying the Hadronic and Leptonic Components. The Astrophysical Journal.
• Nagoya University. (n.d.). Unveiling a CENTURY-OLD mystery: Where the Milky Way’s cosmic rays come from.
• O’Neill, M. (2021, August 27). Unveiling a 100-YEAR-OLD ASTROPHYSICS Mystery: Where the Milky Way’s cosmic rays come from. SciTechDaily.
• Williams, M. (2021, August 27). Astronomers locate the source of High-energy cosmic rays. Universe Today.
