The Hertzsprung–Russell Diagram

The Hertzsprung–Russell diagram is a scatter graph of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their spectral types or classifications and effective temperatures. Hertzsprung–Russell diagrams plot each star on a graph measuring the star's absolute magnitude or brightness against its temperature and color.

H-R Diagram

Hertzsprung–Russell Diagram

Simulator courtesy of University of Nebraska-Lincoln
Student Project Illustrate how HR diagrams of star clusters are used to determine the distances and ages of the clusters..