Post by Skull King on Mar 9, 2007 11:27:25 GMT -5
Stars called white dwarfs lie sparsely scattered in the lower left corner. The giant stars–stars of great luminosity and size (see red giant)–form a thick, approximately horizontal band that joins the main sequence near the middle of the diagonal band. Above the giant stars, there is another sparse horizontal band consisting of the supergiant stars. The stars in the lower right corner of the main sequence are frequently called red dwarfs, and the stars between the main sequence and the giant branch are called subgiants. The significance of the H-R diagram is that stars are concentrated in certain distinct regions instead of being distributed at random. This regularity is an indication that definite laws govern stellar structure and stellar evolution. In population I regions (see stellar populations) like the spiral arms of galaxies or open star clusters, the stars fall almost exclusively on the main sequence.
