Hertzsprung-Russell diagram

The Hertzsprung-Russel diagram is the classification of stars according to their absolute magnitude and temperature.

These parameters, which are not independent,can be used to classify stars into a small number of families. There are main sequence stars, white dwarfs, blue giants, red giants (cold and bright) and supergiants.

Using this diagram, the evolution of stars can be visualised: stars in the main sequence are those inside which only hydrogen is being consumed by nuclear reactions. In red giants, the hydrogen has been consumed in the centre of the star, which collapses. White dwarfs are one of the final stages in the evolution of certain stars.

(Credit: CSIRO Australia 2004).

The evolution of stars in the main sequence can be seen in the HR diagram below.

(Credit: CSIRO Australia 2004).