Hertzsprung–Russell diagram
![Hertzsprung–Russell diagram with 22,000 stars plotted from the Hipparcos Catalogue and 1,000 from the Gliese Catalogue of nearby stars. Stars tend to fall only into certain regions of the diagram. The most prominent is the diagonal, going from the upper-left (hot and bright) to the lower-right (cooler and less bright), called the main sequence. In the lower-left is where white dwarfs are found, and above the main sequence are the subgiants, giants and supergiants. The Sun is found on the main sequence at luminosity 1 (absolute magnitude 4.8) and B−V color index 0.66 (temperature 5780 K, spectral type G2V).](/Images/godic/202501/18/HRDiagram1344.png")
![An HR diagram showing many well known stars in the Milky Way galaxy.](/Images/godic/202501/18/Hertzsprung-Russel_StarData1344.png")
![HR diagrams for two open clusters, M67 and NGC 188, showing the main-sequence turn-off at different ages.](/Images/godic/202501/18/Open_cluster_HR_diagram_ages1344.gif")
![An HR diagram with the instability strip and its components highlighted.](/Images/godic/202501/18/HR-diag-instability-strip.svg1344.png")
The Hertzsprung–Russell diagram, abbreviated H–R diagram or HRD, is a scatter graph of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their spectral classifications or effective temperatures. More simply, it plots each star on a graph measuring the star's brightness against its temperature (color). It does not map any locations of stars.