摘要
It was pointed out that Type Ⅱ supernovae would develop instabilities and asymmetric structure during its explosion. SN1987A, for the first time, provided direct and convincing observational evidence of such behavior. SN1993J confirmed this, too. On July 12, 1993, we obtained a low resolution (5.3 /pixel) spectrum of SN1993J using the 2.16 m telescope in Beijing Astronomical Observatory. We found that many fine structures appeared in the [OI] and H_x lines. This showed that clumping, chemical mixing and strong instabilities had occurred in the ejecta
