Harvard spectrum classification-the abscissa of Herro diagram is the type of spectrum, which is O, B, A, F, G, K, M and other types from left to right according to the order of temperature. It was developed by the Observatory of Harvard University, so it is called Harvard Classification. Starting from 1894, Harvard University Observatory began to systematically classify the spectra of stars. Under the auspices of Anne Cannon, the spectra of hundreds of thousands of stars in 1934 were analyzed for 40 years, and the Henry Draber Catalogue and its extended catalogue in volume 10 were compiled, and the Morgan-Kenner Catalogue now in use was exhibited.
Type Temperature Typical Chromophore (Solar Mass) Radius (Solar Radius) Photometric Hydrogen Line Main Sequence Star Ratio %[7]
Blue ≥16m ☉≥ 6.6r ☉≥ 3 *104l ☉ weak ~0.00003% over o 30000k ~.
B 10000 ~ 30000k blue and white 2.1~16m ☉1.8 ~ 6.6r ☉ 25 ~ 30000l ☉ General 0./kloc-0.
A 7500 ~ 1 10,000 k light blue and white1.4 ~ 2.1m ☉1.4 ~1.8r ☉ 5 ~ 25l ☉ 0.6% stronger.
F 6000 ~ 7500k white1.04 ~1.4m ☉1.15 ~1.4r ☉1.5 ~ 5l ?
G5,200 ~ 6000 k yellow 0.8 ~1.04m ☉ 0.96 ~1.15r ☉ 0.6 ~1.5l ☉ weak 7.6%.
K 3700 ~ 5200k orange 0.45~0.8 M☉ 0.7~0.96 R☉ 0.08~0.6 L☉ Very weak 12. 1%.
M 2200 ~ 3700k red 0.08 ~ 0.45m ☉ 0.2 ~ 0.7R ☉ 5 *10-7 ~ 0.08L ☉ very weak 76.45%.