The spectral type of a star consists of 4 parts:
unknown Ia Iab-b II III/IV V Ia-O Ia/ab Ib II/III IV V/VI Ia-O/Ia Iab Ib-II III IV/V VI
Each of them is represented by one or more letters placed after temperature and luminosity classes:
variable spectrum | : | v |
spectrum with emission lines | : | e |
spectrum interpreted like a shell star | : | sh |
peculiar spectrum | : | p |
spectrum with peculiar profile: | ||
sharp | : | s |
nebulous | : | n |
very nebulous | : | nn |
spectrum with peculiar elements: | ||
peculiar CN | : | CN |
weak line | : | w |
metallic lines | : | m |