In the nineteenth century large-scale photographic spectroscopic surveys of stars were performed at Harvard College Observatory, producing spectral classifications for tens of thousands of stars, culminating … See more

There are several forms of the Hertzsprung–Russell diagram, and the nomenclature is not very well defined. All forms share the same general layout: stars of greater luminosity … See more

Contemplation of the diagram led astronomers to speculate that it might demonstrate stellar evolution, the main suggestion being that stars collapsed from red giants to dwarf stars, then moving down along the line of the main sequence in the course of … See more

Most of the stars occupy the region in the diagram along the line called the main sequence. During the stage of their lives in which stars are found on the main sequence line, they … See more

• Asymptotic giant branch – Stars powered by fusion of hydrogen and helium in shell with an inactive core of carbon and oxygen
• Galaxy color–magnitude diagram – Chart depicting the … See more

• Omega Cen H-R animation of a Hertzsprung–Russell diagram created from real Hubble data
• JavaHRD an interactive Hertzsprung–Russell diagram as a Java applet See more