COLOURMAGNITUDE DIAGRAM

Superposition of colour-luminosity arrays of several galactic clusters and of one globular cluster in astronomy, graph showing the relation between the absolute magnitudes (brightnesses) of stars and their colours, which are closely related to their temperatures and spectral types. It is similar to the Hertzsprung-Russell diagram except that the latter plots spectral types instead of colours and is therefore restricted in its use to relatively nearby stars for which reliable spectra can be obtained.