H-R Diagrams

Astronomers track stellar evolution using a tool called the HR diagram. Some would even call this tool “the most important graph in all of astronomy.” Watch the video HR Diagrams - Part 1, which introduces the basic structure of the HR diagram.
We’ve already seen how measuring the luminosity and temperature of a star can tell us about its mass and radius. Let’s see how that plays out on the HR Diagram. Watch the video HR Diagrams - Part 2.
Now watch HR Diagrams - Part 3 to see how plotting stars on an HR Diagram helps us categorize stars.
Read 18.4 The H–R Diagram to review the significance of the Hertzsprung–Russell diagram in plotting stellar luminosity against surface temperature, and how it helps classify stars based on their evolutionary stage.