  The colour of a star is an indication of its temperature. Blue is the hottest... these stars burn very fast, and have a lifetime measured in millions of years (only a thousandth of the sun's lifetime). The sun is yellow, as are the majority of stars. The 'coolest' stars are red. This is a little misleading, since red giants and supergiants are only cooler in their giant outer layers ... their cores are white hot. It is possible to tell a lot about what chemical elements are in a star, just from the light they give off. This is done by passing the light received from the star through a prism, which splits the light into its component colours. This 'rainbow' is called a spectrum, and contains information about the star that produced the light. |