Stellar classification is a classification of stars based on their spectral characteristics. Most stars are currently classified using the letters O, B, A, F, G, K and M, where O stars are the hottest and the letter sequence indicates successively cooler stars up to the coolest M class. According to an informal tradition, O stars are "blue", B "blue-white", A stars "white", F stars "yellow-white", G stars "yellow", K stars "orange", and M stars "red." The spectrum letter designation is further enhanced by a numerical addition of 0-9 for tenths of the range between two star classes. [ - ]

Stellar classification is a classification of stars based on their spectral characteristics... [ + ]