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A capital letter with a digit subdivision.
Also known as: Spectral type, OBAFGKM sequence
The notation classifying a star by its spectrum, running through a fixed letter sequence from hottest to coolest.
Classifies a star by its spectrum, the letter sequence running from hottest to coolest.
Contexts: History
Runs in a famously unalphabetical order because the classes were originally lettered by the strength of hydrogen lines and only later reordered by temperature, with the unused letters dropped.
Contexts: History
A capital letter followed by a digit from zero to nine subdividing the class.