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The Hertzsprung-Russell diagram plots stars by which two properties?

Luminosity and surface temperature (or spectral class).

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  1. Mass and distance
  2. Luminosity and surface temperature ✔
  3. Age and color index only

Why: Ejnar Hertzsprung (1911) and Henry Norris Russell (1913) independently plotted star brightness against spectral class. They found temperature and luminosity are related, and most stars fall on a band called the main sequence.

Huh, didn't know that: Russell's Princeton work was so strong the faculty created a new honors level above summa cum laude for him.

The dad joke
Why do astronomers love the H-R diagram? Because it plots out their whole future.
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References

Answer: Luminosity and surface temperature. Ejnar Hertzsprung (1911) and Henry Norris Russell (1913) independently plotted star brightness against spectral class. They found temperature and luminosity are related, and most stars fall on a band called the main sequence.

  1. Astronomy 2e, 18.4 The H-R Diagram openstax.org/books/astronomy-2e/pages/18-4-the-h-r-diagram
    led to the extremely important discovery that the temperature and luminosity of stars are related
    Checked 2026-10-10.

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