Hertzsprung-Russell diagram

In astronomy, graph on which the surface temperatures of stars are plotted against their luminosities. Most stars, including the Sun, fall into a narrow band called the main sequence. When a star grows old it moves from the main sequence to the upper right part of the graph, into the area of the giants and supergiants. At the end of its life, as the star shrinks to become a white dwarf, it moves again, to the bottom left area. It is named after the Danish astronomer Ejnar Hertzsprung and the US astronomer Henry Russell, who independently devised it in the years 1911–13.