With a new observatory, a team of Chinese astronomers has found over a dozen sources of ultra-high-energy cosmic rays. And these sources do not come from a distant, exotic corner of the cosmos. They come from our own backyard.
Ultra-high energy cosmic rays (UHECR) are… quite energetic, typically a million times more energetic than our most powerful particle accelerators. They are also relatively rare, and as a result, astronomers have had difficulty pinpointing their origin.
But a team of Chinese scientists led by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences has dug deep into the origins of UHECRs with the recently built Large High Altitude Air Shower Observatory (LHAASO). LHAASO is currently being built in Daocheng, southwest China’s Sichuan Province, but the astronomers were able to use the completed half of the instrument for an eleven-month observation run.
They found a dozen sources of UHECRs as well as a few 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 of these sources are in the Milky Way.
“These findings change our traditional understanding of the Milky Way and open an era of UHE gamma astronomy. These observations will lead us to rethink the mechanism by which high-energy particles are created and diffused in the Milky Way, ”said Cao Zhen, LHAASO chief scientist.
“In addition, these observations will encourage us to explore violent celestial phenomena and their physical processes more deeply, as well as to test basic physical laws under extreme conditions,” said Cao.
The sources of the UHECRs include a multitude of nature’s own particle accelerators: newly formed giant stars, supernova explosions, massive star clusters, pulsar wind nebulae and more.
The entire LHAASO facility will be completed in 2021. “With the completion of LHAASO and the continuous collection of data, we can expect to find an unexplored ‘UHE universe’ full of surprising phenomena,” added He Huihai of IHEP.