A Powerful Gamma Ray Burst . ... Credit Copyright: S. R. Kulkarni, S. G. Djorgovski ( Caltech ), the Caltech GRB Team , NASA Explanation: Gamma-ray bursts are thought to be the most powerful explosions in the Universe, yet the cause of these high-energy flashes remains a mystery . Blindingly bright for space-based gamma-ray detectors the burst sources are so faint at visible wavelengths that large telescopes and sensitive cameras are required to search for them. ... NASA Official: Jay Norris. ...