Hertzsprung-Russell Diagram

Scientists have discovered many different kinds of stars - from dwarfs to supergiants, from "normal" to cepheids. But up until the early 1900's, there was no general way to classify them. That all changed with the invention of the Hertzsprung-Russell Diagram, which has become one of the most important tools in stellar astronomy. This section talks about its history, uses, and provides a few sample ones.