Unit 7 Minilecture 4: The H-R Diagram

This minilecture introduces the Hertzsprung-Russell Diagram, or H-R diagram. We learn what quantities we can plot in the diagram and how we can determine the radii of stars from the H-R diagram. Finally, we end by comparison of the relative sizes of stars, from behemoth red supergiants through miniscule white dwarfs. Table of Contents: 00:23 - If you see a trend in a graph, there is often (but not always!) a relationship between the two things. 03:34 - Stefan-Boltzmann Law: The luminosity of a blackbody depends on its temperature AND its size. 04:11 - The Hertzsprung-Russell (H-R) diagram plots a star's temperature against its luminosity. 07:27 - 08:27 - Most stars fall somewhere on the main sequence of the H-R diagram. 08:52 - Stars with lower temperatures and higher luminosities than main-sequence stars must have larger radii. These stars are called giants and supergiants. 09:13 - Stars with higher temperature and lower luminosities than main-sequence stars must have smaller radii. These stars are called white dwarfs. 09:34 - The H-R diagram is a plot of temperature against luminosity, but also tells us the radius of a star. 10:35 - The Relative Sizes of Stars 14:02 - Summary: The H-R Diagram