Spectra
When a supernova is observed, it can be categorized in the Minkowski–Zwicky supernova classification scheme based upon the absorption lines that appear in its spectrum. A supernova is first categorized as either a Type I or Type II, then sub-categorized based on more specific traits. Supernovae belonging to the general category Type I lack hydrogen lines in their spectra; in contrast to Type II supernovae which do display lines of hydrogen. The Type I category is sub-divided into Type Ia, Type Ib and Type Ic supernovae.
Type Ib/Ic supernovae are distinguished from Type Ia by the lack of an absorption line of singly ionized silicon at a wavelength of 635.5 nanometres. As Type Ib/Ic supernovae age, they also display lines from elements such as oxygen, calcium and magnesium. In contrast, Type Ia spectra become dominated by lines of iron. Type Ic supernovae are distinguished from Type Ib in that the former also lack lines of helium at 587.6 nm.
Read more about this topic: Type Ib And Ic Supernovae