One Step Closer to Understanding Cosmic Rays: Scientists Explain Origin of Highest-Energy Particles in the Universe

Scientists from Nagoya University measured the protons and electrons from cosmic rays in a supernova remnant in a bid to find where the highest-energy particles in the universe come from.

For over a century, the origin of cosmic rays is one of the mysteries of high-energy astrophysics that have remained unsolved up to this day. Several studies have defined and described the highest-energy particles in the universe, but none has given a definite answer to this 100-year-old question.

Nagoya University scientists have currently quantified protons and electrons in cosmic rays from a supernova remnant for the first time. Their full findings were published in their study titled "Pursuing the Origin of the Gamma Rays in RX J1713.7-3946 Quantifying the Hadronic and Leptonic Components" in The Astrophysical Journal.

Solving the 100-Year-Old Mystery

Cosmic rays were first discovered in 1912. According to the news release from Nagoya University, novel imaging analysis of radio, gamma-ray radiation, and X-ray reveal that at least 70% of very-high-energy gamma rays from cosmic rays are due to relativistic protons.

The study is the first to quantitatively show the number of cosmic rays produced in a supernova remnant, bringing scientists one step closer to finding the origin of cosmic rays. Understanding where the highest-energy particles come from is an important step in understanding the evolution of the Milky Way galaxy.

Previous studies have shown that several supernova remnants emit gamma rays at teraelectronvolts (TeV) energies. Scientists believe that if protons produce gamma rays, the main component of cosmic rays, they will prove the origin of cosmic rays. However, the team had to test whether cosmic rays have dominant protons or electrons since they are not made purely with the former.

The study provides significant evidence that gamma rays originated from the proton component and clarifies that supernova remnants produce cosmic rays. They showed that protons account for 70% of the total gamma rays, while electrons account for 30%.

The findings demonstrate that proton origins of gamma rays are dominated in interstellar gas-rich regions of the universe, while electron origins of gamma rays dominate in the gas-poor regions. This shows that protons and electrons work together to support the predictions of past theoretical studies.

Cosmic Rays Key to Understanding Origin of the Galaxy

As Science Daily reported, cosmic rays are charged subnuclear particles that move at almost the same rate as the speed of light. Albert Einstein's special relativity explains that these particles are relativistic and can manage to generate a magnetic field that controls where they move within the galaxy.

Alexandre Marcowith from the University of Montpellier said that cosmic rays might help explain the origin of the galaxy and the aspects within it. Supernova shockwaves accelerate cosmic rays and stream them away, which may have contributed to generating magnetic field seeds required to the actual magnetic field around us.

Plasma waves scatter cosmic rays, and their instability is associated with the collective streaming motion of cosmic rays. This might be the source of this astrophysical phenomenon, showing how they play a role in the Milky Way.