Earth and Space Science / Unit 10: Stars, Galaxies and the Universe
10.2 The H-R Diagram
Notes
The Hertzsprung-Russell (H-R) diagram plots stars by luminosity (vertical, brighter at top) and surface temperature (horizontal, hotter on the left).
- The main sequence is a band from hot, bright stars (upper left) to cool, dim stars (lower right). About 90% of stars, including the Sun, are on it.
- Red giants and supergiants are cool but very luminous because they are huge (upper right).
- White dwarfs are hot but dim because they are tiny (lower left).
- On the main sequence, more massive stars are hotter and brighter but live shorter lives.
Practice
On the H-R diagram, a star that is cool but very luminous must be:
Large surface area makes up for low temperature.
A hot, dim star in the lower left is most likely a:
White dwarfs are small and hot.
The Sun is on the:
It is fusing hydrogen in its core like most stars.
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