SN 1961I

SN 1961I was a Type Ib supernova observed in the galaxy NGC 4569 (Messier 90) in the constellation Virgo. It was discovered in May 1961, reaching a peak magnitude of approximately 13.0. The "SN" designation stands for SuperNova, and the following number indicates the year of discovery, with the letter denoting the chronological order of supernova discoveries within that year. Therefore, SN 1961I was the ninth supernova discovered in 1961.

Type Ib supernovae are a subtype of core-collapse supernovae that result from the explosion of massive stars that have lost most of their outer hydrogen envelope before exploding. This loss of hydrogen can occur through stellar winds or mass transfer to a companion star in a binary system. Consequently, their spectra lack strong hydrogen lines, unlike Type II supernovae, but show prominent helium lines early in their evolution. The progenitor star of SN 1961I is believed to have been a massive Wolf-Rayet star or a similar evolved, stripped-envelope star.

The study of SN 1961I, along with other early-discovered supernovae, has been crucial in developing our understanding of stellar evolution, the processes of core-collapse supernovae, and the chemical enrichment of galaxies. Its light curve and spectral properties provided valuable data for characterizing Type Ib supernovae and distinguishing them from other types of stellar explosions. Observations of SN 1961I have contributed to our understanding of the diversity within the Type Ib class and the various evolutionary pathways that lead to such events.