Prounciation: [hertshprung]

The graphical representation of the correlation between the spectrum and luminosity for a sample of stars, discovered independently by Danish astronomer Ejnar Hertzsprung (1873–1967) and US astronomer Henry Norris Russell (1877–1957). The diagram achieves its astrophysical significance when the plotted points are restricted to a particular sample (such as all the members of a star cluster) or a particular type (such as one class of variable star). It then effectively graphs surface temperature against luminosity. In the diagram, normal stars that are burning hydrogen form a broad band known as the main sequence. Evolved stars clump together as red giants. Almost defunct stars are grouped as white dwarfs. The theory of stellar evolution explains the main features of the diagram.

luminosity, main sequence, Russell, H N, spectrum, star (astronomy), stellar evolution