Stellar Plot

One of astronomy's most powerful tools is the Hertzsprung-Russell diagram, which plots a star's brightness against its temperature. The diagram reveals patterns that tell us how stars work. The curved line across the middle of the diagram forms the main sequence, which comprises stars that are in the prime of life, "burning" the hydrogen in their cores to make helium. Near the ends of their lives, the stars puff up to form giants or supergiants, which are plotted at the upper right. (The Sun will become a giant in a few billion years.) The final remnants of most stars, including the Sun, are white dwarfs, at lower left, which are hot but dead stellar cores. [ESO]