World : Highest-Energy Photons Ever Detected Have Been Traced to an Enigmatic Source

It may have exploded nearly a thousand years ago, but the Crab Nebula is still spitting out radiation at incredibly high energies. In fact, astronomers have detected record-breakingly energetic photons coming from the object, clocking in at up to 450 trillion electron volts.

Previously, the highest energy photon ever detected was just 75 trillion electron volts, or teraelectronvolts (TeV). This marks the first time astronomers have detected such high energy photons - known as gamma rays- over 100 TeV.

The detection was made at ASgamma, a facility jointly run by China and Japan in Tibet. In 2014, it was upgraded to add underground water Cherenkov muon detectors; since then, they have made 24 gamma ray detections between 100 and 450 TeV.

For context, particles from the Sun are usually below 1 billion electronvolts, or GeV.

"This is the very first but a great step forward," said physicist Jing Huang of the Chinese Academy of Sciences. "It proves that our techniques worked well, and gamma rays with energies up to a few hundred TeV really exist."

When traced back to their source, these gamma rays seem to point directly to the Crab Nebula, a supernova remnant 6,500 light-years away, with the pulsing remains of a dead star in its centre - the Crab Pulsar.

This object is one of the most famous dead stars in the Milky Way, because it was the first in which a supernova remnant - the nebula itself - was traced to historical observations of a supernova. In 1054 CE the exploding star, which was bright enough to be seen during the day, was observed and recorded by Chinese astronomers.

 

Source : https://www.sciencealert.com/the-highest-energy-photons-ever-have-been-detected-coming-from-the-crab-nebula

Smart Grid Bulletin September 2019


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