SN 1993J

SN 1993J is a supernova that was observed in the galaxy M81 (also known as Bode's Galaxy) in 1993. It was discovered on March 28, 1993, by amateur astronomer Francisco Garcia Diaz of Spain. Its proximity and brightness made it one of the most studied supernovae of the 20th century, providing crucial data for understanding the mechanisms behind stellar explosions and their evolution.

SN 1993J is classified as a Type IIb supernova. This designation indicates that the progenitor star was likely a massive star that had lost most of its hydrogen envelope before core collapse. Initially, the spectrum showed strong hydrogen lines, characteristic of a Type II supernova. However, over time, these hydrogen lines faded, and helium lines became more prominent, classifying it as a Type IIb supernova.

The progenitor star is believed to have been a red supergiant star in a binary system. The interaction with its companion is thought to have stripped away much of its outer hydrogen layer. The core collapse triggered the supernova explosion.

Observations of SN 1993J provided valuable insights into the physics of supernovae, including the mixing of elements within the ejecta, the formation of dust in the expanding supernova remnant, and the interaction of the supernova with the surrounding circumstellar medium. Its detailed light curve and spectral evolution have been used to refine models of supernova explosions and the evolution of massive stars. The remnant continues to be observed at various wavelengths, providing further data on the long-term effects of the explosion.