High Quality Content by WIKIPEDIA articles! GRB 970508 was a gamma-ray burst (GRB) detected on May 8, 1997, at 21:42 UTC. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths (X-ray, ultraviolet, optical, infrared, and radio).