Henrietta Leavitt

Astronomer whose discovery of the period-luminosity relation for Cepheid stars revolutionized cosmic distance measurement.

Henrietta Swan Leavitt (1868–1921), a Harvard College Observatory "computer," made groundbreaking contributions to astronomy despite gender barriers. Tasked with cataloging stars, she analyzed thousands of variable stars in the Magellanic Clouds. Her 1912 discovery that Cepheid variable stars have predictable brightness cycles (period-luminosity relation) enabled astronomers to measure interstellar distances.

Leavitt's work laid the foundation for modern cosmology. Edwin Hubble used her findings to prove the Milky Way was not the only galaxy, sparking the concept of an expanding universe. Yet, as a woman in science, she received little recognition during her lifetime and was paid 30 cents per hour for her work.

Today, Leavitt is celebrated for giving us the yardstick to measure the universe, as George Johnson wrote in Miss Leavitt’s Stars. Her story highlights marginalized voices in STEM and reshapes narratives about who belongs in scientific discovery.