| Event type | Gamma-ray burst  |
|---|---|
| Constellation | Leo |
| Right ascension | 10h 44m 49.95957s |
| Declination | +21° 31′ 17.4375″ |
| Distance | 587,000,000 pc (1.91×109 ly) |
| Other designations | GRB 030329A, GRB 030329, SN 2003dh |
GRB 030329 was a gamma-ray burst (GRB) that was detected on 29 March 2003 at 11:37 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). GRB 030329 was the first burst whose afterglow definitively exhibited characteristics of a supernova, confirming the existence of a relationship between the two phenomena.