Astronomers Have Tracked Down the Source of High Energy Cosmic Rays to Regions Within the Milky Way Itself

Using a new observatory, a team of Chinese astronomers have found over a dozen sources of ultra-high energy cosmic rays. And those sources aren’t from some distant, exotic corner of the cosmos. They come from our own backyard.

Ultra-high energy cosmic rays (UHECR’s) are…pretty energetic, typically millions of times more energetic than our most powerful particle accelerators. They are also relatively rare, and so astronomers have had a hard time pinpointing their origins.

But a team of Chinese scientists led by Institute of High Energy Physics (IHEP) under the Chinese Academy of Sciences dug deep into the origins of UHECR’s using the recently-built Large High Altitude Air Shower Observatory (LHAASO). LHAASO is currently under construction in Daocheng in southwest China’s Sichuan Province, but the astronomers were able to use the completed half of the instrument for an 11-month observation run.

They found a dozen sources of UHECR’s, as well as some high-energy photons, including one with an energy of 1.4 Peta-electron volts (quadrillion electron-volts or PeV), the most energetic photon ever observed.

All those sources sit within the Milky Way.

“These findings overturn our traditional understanding of the Milky Way and open up an era of UHE gamma astronomy. These observations will prompt us to rethink the mechanism by which high-energy particles are generated and propagated in the Milky Way,” said Cao Zhen, chief scientist of LHAASO.

“In addition, these observations will encourage us to explore more deeply violent celestial phenomena and their physical processes, as well as to test basic physical laws under extreme conditions,” Cao said.

The sources of the UHECR’s include a variety of nature’s own particle accelerators: newly-formed giant stars, supernovae explosions, massive star clusters, pulsar wind nebulae, and more.

The entire facility of LHAASO will be completed in 2021. “With the completion of LHAASO and continuous data accumulation, we can anticipate finding an unexplored ‘UHE universe’ full of surprising phenomena,” He Huihai with the IHEP added.