The Birth of Gamma-Ray Burst Astronomy:

Gamma-Ray Bursts (GRBs) are some of the most energetic events in the universe. Unsurprisingly, they have been of great interest to the scientific community since their initial discovery in the 1960"s. GRBs are broken up into two types: Short Gamma-Ray Bursts (SGRB) and Long Gamma-Ray Bursts (LGRB). SGRB are observed bursts that are shorter than 2 seconds, and LGRB are observed bursts that are longer than 2 seconds. It was discovered in 1993 that these two subclasses of GRBs existed; however, at that time, the cause of the two different sub types was unknown.

To learn about these GRBs, see:
http://www.fromquarkstoquasars.com/the-birth-of-gamma-ray-burst-astronomy/

Image source:
http://chandra.harvard.edu/photo/printgallery/2004/