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Who discovered the cepheid period-luminosity relation in 1908?

Henrietta Leavitt, at Harvard College Observatory.

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  1. Annie Cannon
  2. Henrietta Leavitt ✔
  3. Vera Rubin

Why: Leavitt studied variable stars in the Magellanic Clouds. Since those stars are all at about the same distance, brighter-looking cepheids had to be truly brighter, and they had longer periods.

Huh, didn't know that: Her relation later let Edwin Hubble measure the distance to other galaxies.

The dad joke
Leavitt found stars with rhythm. You could say she discovered the universe's beat.
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References

Answer: Henrietta Leavitt. Leavitt studied variable stars in the Magellanic Clouds. Since those stars are all at about the same distance, brighter-looking cepheids had to be truly brighter, and they had longer periods.

  1. OpenStax Astronomy 2e, 19.3 Variable Stars openstax.org/books/astronomy-2e/pages/19-3-variable-stars-one-key-to-cosmic-distances
    The relation between period and luminosity was discovered in 1908 by Henrietta Leavitt
    Checked 2026-10-10.

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