GRB 991216, nicknamed the Beethoven Burst by Dr. Brad Schaefer of Yale University, was a gamma-ray burst observed on December 16, 1999,[1] coinciding with the 229th anniversary of Ludwig van Beethoven's birth.

[2] 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).

[1] Frank Marshall, a NASA astrophysicist at the Goddard Space Flight Center, commented that "this was by far the brightest burst we have detected in a long time.

[4] The analysis of the observations strengthened the theory that gamma-ray bursts are a result of a hypernova,[5] though other possible progenitors exist, such as the merger of two black holes.

[6] This rapid determination allowed astronomers to conduct follow-up studies using optical and X-ray telescopes.