That’s a classification scheme created by Annie Jump Cannon in the early 1900s based on stellar spectra.

这是 Annie Jump Cannon 在 1900 年代初期根据恒星光谱创建的分类方案。

The classification scheme proposed by Cannon and decoded by Payne-Gaposchkin is still used today, and arranges stars by their temperature, assigning each a letter.

由加农提出并经佩恩-加波斯金解译的分类方案至今仍在使用，它根据恒星的温度将他们进行排列，并给每颗星星都分配了一个字母代号。