GENERAL KNOWLEDGE

Detailed explanation-1: -The main spectral classes in order from hottest to coolest are O, B, A, F, G, K, and M. These classes have particular colors. Spectral type is most often written across the top of the H-R diagram going from hot, bluer “O” stars on the left to cool, more red “M” stars on the right.

Detailed explanation-2: -The classes are called O, B, A, F, G, K and M. Stars in the ‘O’ class are the most massive and hottest, with temperatures above 30, 000 °C. Stars in the ‘M’ class are the smallest and coolest, with temperatures below 3, 000 °C.

Detailed explanation-3: -Type O stars have the highest surface temperatures and can be as hot as 30, 000 Kelvins.