Stellar Astronomy: Part 3 – Classes and the Main Sequence

With the technology available in the nineteenth and twentieth centuries, astronomers made a number of wonderful discoveries about the nature of stars.  These included knowledge of the true luminosity of stars as well as their chemical composition and temperature.  Although all stars have a similar chemical composition, they come in a wide variety of luminosities and temperatures.  As more stars were catalogued, astronomers began to notice a pattern.  Secular, evolutionary thinking led to some false interpretations about the cause of this pattern.  This lesson in history is an important one for us today.