Classification of the Stars

Abstract

Classification of the stars has come a long way since Hipparchus designated the first stars to “come out at night” as the brightest, to the modern and often colorful Hertzsprung–Russell diagram. You can create your own H–R diagram as shown. A brief history is given for the development of star classes from Euclid to the important contribution of Annie Jump Cannon. It is easy to ask for a true color and a false color picture, but, as the discussion of how the eye works shows, true color is hard to define. Spectroscopy, the (B–V) color index, provides a science-based solution to accurately classify what is being seen or photographed. Spectroscopy also reveals the chemical composition of all those distant suns.