Gamma-ray burst

Gamma-ray bursts (GRBs) are immensely energetic but rare electromagnetic cosmic explosions releasing around 1043W to 1047W. These can be caused by various cosmic events like a supernova or hypernova, a merger of neutron stars, a black hole formation, a magnetar, or a tidal disruption event when a star interacts with a supermassive black hole.

A typical cosmic burst releases as much energy in a few seconds as the Sun will in its entire 10-billion-year lifetime and are extremely rare (a few per galaxy per million years). A GRB event in the Milky Way, pointing directly towards the Earth, could cause a mass extinction event. The major Ordovician–Silurian extinction events 450 million years ago may have been caused by a GRB.

They could also be on a much smaller scale, such as the short bursts during EMPs.