Type Ien supernova

A Type Ien supernova is a proposed type of supernova event. It is characterized by having spectra that are dominated by elements such as ionized silicon, sulphur and argon while at the same time lacking prominent features from elements such as carbon, oxygen, helium and hydrogen.
This type of supernova was made by the discovery of SN 2021yfj in 2021 who's emission lines were unique compared to other supernova. It also means that a placeholder intermediate type of supernova named Type [Idn supernova|SN Idn] could exist and would have its spectra be dominated by either oxygen, neon or magnesium.