Hertzsprung-Russel diagram or HR diagram is a scatter plot or a graphical tool that is used by astronomers to classify stars based on their luminosity, color, temperature, spectral type and also the stage of evolution.
The HR diagram plots the temperature of the stars against the luminosity, or the color of starts against absolute magnitude.
The HR diagram is divided into stages, for example those stars at the stable phase of hydrogen burning are found within the main sequence according to their mass.
