The H–R Diagram

Mapping every kind of star

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• $L/L_\odot = (R/R_\odot)^2 (T/5772\text{ K})^4$: luminosity depends on size and temperature.
• The H–R diagram plots luminosity against temperature (hot on the left).
• Main sequence: hydrogen-burning stars, ordered by mass. Giants are top right; white dwarfs bottom left.
• Main-sequence lifetime $\propto M^{-2.5}$: heavy stars die young.

Steps

1. Same colour, brighter
2. Luminosity, size and temperature
3. Build a star
4. The Pup
5. The main sequence
6. A heavier star