Astronomy on MSN

What is the origin of the letters used in star classification?

What is the origin of the letters used in star classification? Why didn't astronomers use ABCD? J. HaldimanChicago, Illinois ...
Astronomy

Color-coding stars

Stellar spectral classification utilizes seven main classes (O, B, A, F, G, K, M), ordered by decreasing surface temperature, with each class further subdivided into numerical subclasses (0-9) ...