In the professional spectral classification mnemonic 'O B A F G K M,' which letter represents the coolest stars?

Answer

M

In the spectral sequence, stars classified as 'O' are the hottest and bluest, while 'M' stars are the coolest and reddest.

In the professional spectral classification mnemonic 'O B A F G K M,' which letter represents the coolest stars?
astronomytemperatureheatcolorstar