Introduction

The study of the stars began in earnest toward the end of the eighteenth century with the work of William Herschel. Herschel sought among the stars some kind of order, something as profound as the regularities Copernicus, Kepler, and Newton had found in the solar system. Like a pioneer in any other branch of science, Herschel began with observation and spent many years cataloging stars and measuring their apparent motions. From this study he was able to arrive at a structure for the universe that is not far from the one that today's astronomers believe to be correct.

Of the billions of stars in the universe, none (besides the sun) appears as more than a point of light to even the most powerful telescope. As recently as the last century most scientists despaired of ever knowing the physical nature of the stars. Today, however, thanks to spectroscopic analysis, we not only have a great deal of detailed information on thousands of stars but also are able to trace the evolution of a star from its birth through maturity to its last agonies and eventual "death."