A flash of the most energetic and violent gamma and X-rays hit our planet at the beginning of last October. If we did not notice it, or rather, if it was mainly the sensors of the instruments scanning the sky that noticed it, it is because the flash came from deep space, from a distance, and a time, incredibly far away: two billion light years, so the rays took two billion years to reach Earth. Far away, agreed, but not for everyone: for astronomers, 2 billion light years are not that many and, indeed, according to scientists who study stars, this is the closest flash ever recorded.
Gamma bursts are extremely fast flashes of energy caused by the collision of neutron stars or the explosion of massive stars that occur when they deplete the nuclear fuel that keeps them alive. The amount of energy emitted in a few seconds is immense: equal to that which a star like our Sun produces during its long existence, i.e. 12 billion years.