How two gamma-ray bursts created record-breaking high-energy photons
Two eruptions of gamma rays from exploding stars in far-off galaxies have pelted Earth with the highest-energy photons yet detected from one of these explosions. The shower of light particles reveals how so-called long gamma-ray bursts — among the most powerful explosions in the universe — produce such energetic photons. “This is the Rosetta Stone of gamma-ray bursts,” says Tsvi Piran, an astrophysicist at the Hebrew University of Jerusalem who was not involved with this research. Long gamma-ray bursts, or GRBs, mark the death of a massive star as it explodes and leaves behind a neutron star or a black hole. (Short GRBs, on the other hand, accompany collisions between neutron stars, such as the smashup picked up by gravitational-wave detectors in 2017 (SN: 10/16/17).) Until now, the most energetic photons radiating from a long GRB typically maxed out at a few million electron volts of energy, or roughly a million times more energetic than the photons our eyes detect. That record has...