Researchers at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), part of the SLAC National Accelerator Laboratory, have confirmed that cosmic rays are created in the aftermath of supernovas, a theory that had never before been proven conclusively.

The team of researchers, led by Assistant Professor of Physics Stefan Funk, analyzed four years of data from NASA’s Fermi Gamma-ray Space Telescope. The researchers found that the aftermath of two supernovas had accelerated protons through a process called Fermi acceleration, causing these protons to transform into cosmic rays.

Scientists had previously believed that cosmic rays were created either by supernovas or through energy from black holes but were unable to find definite evidence because they could not trace the rays back to their source.

The SLAC team approached the issue by looking at gamma rays, which have distinctive signatures and are created when cosmic rays combine with static protons. Unlike cosmic rays, which are deflected by magnetic fields, gamma rays travel in straight lines, and their source can be identified.

“It’s fitting that such a clear demonstration showing supernova remnants accelerate cosmic rays came as we celebrated the 100th anniversary of their discovery,” Kavli Institute Director Roger Blandford said in a press release. “It brings home how quickly our capabilities for discovery are advancing.”

The team’s findings were published in the Feb. 15 issue of Science.