About a century ago, scientists began to realize that some of the radiation we detect in the Earth’s atmosphere is not of local origin.
This eventually led to the discovery of cosmic rays, high-energy protons, and atomic nuclei that have been stripped of their electrons and accelerated to relativistic speeds (close to the speed of light).
However, there are still several mysteries surrounding this strange (and potentially lethal) phenomenon.
This includes questions about its origins and how the main component of cosmic rays (protons) accelerates at such a high speed.
Thanks to new research led by Nagoya University, scientists have for the first time quantified the amount of cosmic rays produced in a supernova remnant.
This research has helped solve a 100-year-old mystery and is an important step toward accurately determining where cosmic rays come from.
Although scientists theorize that cosmic rays originate from many sources (the Sun, supernovae, gamma-ray bursts (GRBs), and galactic active nuclei), their exact origin has been a mystery since were discovered in 1912.
Similarly, astronomers have theorized that supernova remnants (the after-effects of supernova explosions) are responsible for accelerating them to almost the speed of light.
As they travel through our galaxy, cosmic rays play a role in the chemical evolution of the interstellar medium (ISM). As such, understanding their origin is critical to understanding how galaxies evolve.
In recent years, improved observations have led some scientists to speculate that supernova remnants give rise to cosmic rays because accelerating protons interact with ISM protons to create high-energy gamma rays (HEVs).
However, gamma rays are also produced by electrons interacting with ISM photons, which can be in the form of infrared photons or cosmic microwave background radiation (CMB). Therefore, determining which source is larger is paramount in determining the origin of cosmic rays.
Hoping to shed light on it, the research team – which included members of Nagoya University, the National Astronomical Observatory of Japan (NAOJ) and the University of Adelaide, Australia – observed the supernova remnant. RX J1713.7? 3946 (RX J1713).
The key to their research was the new approach they developed to quantify the gamma-ray source in interstellar space.
Previous observations have shown that the intensity of VHE gamma rays caused by the collision of protons with other protons in the ISM is proportional to the density of interstellar gas, which can be discerned by radio line imaging.
On the other hand, the gamma rays caused by the interaction of electrons with photons in the ISM are also expected to be proportional to the intensity of the non-thermal X-rays of the electrons.
For their study, the team relied on data obtained by the High Energy Stereoscopic System (HESS), a VHE gamma-ray observatory located in Namibia (and operated by the Max Planck Institute for Nuclear Physics).
They then combined it with X-ray data obtained by ESA’s Multiple Mirror Mission Observatory (XMM-Newton) and data on gas distribution in the interstellar medium.
They then combined the three data sets and determined that protons accounted for 67 ± 8 percent of cosmic rays, while cosmic ray electrons accounted for 33 ± 8 percent, approximately a 70/30 split.
These findings are innovative as they are the first time that the possible origins of cosmic rays have been quantified. They also constitute the most definitive evidence to date that the remains of supernovae are the source of cosmic rays.
These results also show that gamma rays of protons are more common in gas-rich interstellar regions, while those caused by electrons are improved in gas-poor regions.
This supports what many researchers have predicted, which is that the two mechanisms work together to influence the evolution of ISM.
Professor Emeritus Yasuo Fukui, who was the lead author of the study, said: “This new method could not have been achieved without international collaborations. [It] it will be applied to the remains of supernovae using the new generation CTA (Cherenkov Telescope Array) gamma ray telescope, in addition to the existing observatories, which will allow considerable progress in the study of the origin of cosmic rays. “
In addition to leading this project, Fukui has been working to quantify the distribution of interstellar gas since 2003 using the NANTEN radio telescope at the Las Campanas Observatory in Chile and the Australia Telescope Compact Array.
Thanks to Professor Gavin Rowell and Dr. Sabrina Einecke of the University of Adelaide (co-authors of the study) and the HESS team, the spatial resolution and sensitivity of gamma-ray observatories have finally reached the point where it is possible to do so. comparisons between the two.
Meanwhile, co-author Dr. Hidetoshi Sano of the NAOJ led the analysis of archive data sets from the XMM-Newton Observatory. In this sense, this study also shows how international collaborations and data exchange allow all kinds of cutting-edge research to be carried out.
Along with improved instruments, improved methods, and greater opportunities for cooperation lead to an era in which astronomical advances become a common occurrence.
This article was originally published by Universe Today. Read the original article.