Hertzsprung-Russell diagram

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Hertzsprung-Russell diagram (H-R diagram) Plot of the absolute magnitude of stars against their spectral type; this is equivalent to plotting their luminosity against their surface temperature or colour index. Brightness increases from bottom to top, and temperature increases from right to left. Henry Norris Russell devised the diagram in 1913, independently of Ejnar Hertzsprung, who had the same idea some years before. The H-R diagram reveals a pattern in which most stars lie on a diagonal band, the main sequence.

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