M Stars

M stars are cool stars characterized by the presence of molecular TiO bands. Some VO preesent. 

M Stars: C/O < 1
S Stars: C/O = 1
C Stars: C/O > 1
M2V M8V

M10 M8

M0III M1IIIb

M2III M3III

M4III M5III

M6III M8III

M0II M2II

M4II

M2Iab M2Iape

M3Ib