List of Spectral Classes for Main Sequence Stars
Related article: spectral class spectral class,
in astronomy, a classification of the stars by their spectrum and luminosity. In 1885, E. C. Pickering began the first extensive attempt to classify the stars spectroscopically.
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| Class | Color | Surface Temperature | Strong Lines |
| O | blue-white | 35,000°C; | ionized helium |
| B | blue-white | 21,000°C; | helium |
| A | white | 10,000°C; | hydrogen |
| F | creamy | 7,000°C; | ionized calcium |
| G | yellow | 6,000°C; | calcium |
| K | orange | 4,500°C; | titanium oxide |
| M | red | 3,000°C; | titanium oxide |