https://www.theregister.co.uk/2019/11/21/gamma_ray_bursts/

Scientists have detected the most-energetic photons yet seen from a gamma ray burst, with energies nearing a trillion electron volts.

Gamma ray bursts (GRBs) are the most powerful known explosions in the universe that occur when massive stars collapse into neutron stars or black holes. The spectacle features intense gamma ray plasma jets that eventually fade into an afterglow of energies, ranging from X-rays to radio waves. They’re difficult to study since the source of the flares are often in faraway galaxies, and eggheads haven’t quite figured out what triggers such energetic photons.