Today in the history of astronomy, a major figure in our understanding of variable stars and galaxy shapes is born.
Henrietta Swan Leavitt became one of the most famous Harvard computers, famous for her determination of the period-luminosity law. Credit: Public Domain/Wikimedia Commons
- Henrietta Swan Leavitt was employed by the Harvard College Observatory from 1903 as one of the “Harvard Computers”, specializing in the identification and cataloging of variable stars on photographic plates.
- His most important scientific contribution was the discovery of the period-luminosity relation for variable stars, which demonstrated a direct relationship between a star’s pulsation period and its intrinsic luminosity.
- This fundamental breakthrough provided astronomers with an important tool for measuring cosmic distances, which then enabled Harlow Shapley and Edwin Hubble to determine the size of the Milky Way and confirm the existence of outer galaxies.
- Throughout her career, Leavitt discovered over 2,400 variable stars and became head of the Photographic Photometry Department and continued her work at the observatory until her death in 1921.
Born in Massachusetts on July 4, 1868, Henrietta Swan Leavitt attended Oberlin, the nation’s first co-educational college, before completing her degree at the Society for Collegiate Instruction of Women (today, Radcliffe College). He studied astronomy only in his last year of school. But after volunteering for some time at the Harvard College Observatory (HCO), Edward Pickering hired him as part of his permanent staff in 1903.
As one of the “Harvard Computers”, a group of women who cataloged stars on photographic plates, Leavitt specialized in finding variable stars. For 30 cents an hour, Leavitt compared pairs of plates, searching for fluctuations in brightness that would suggest variable stars. Despite limitations in allowing women to work at HCO, Leavitt excelled, discovering over 2,400 variable stars and becoming head of the Photographic Photometry Department.
Leavitt’s most influential contribution to astronomy was his discovery of the period-luminosity relationship: in essence, a variable star’s period (the time it takes to go from bright to dim) is related to its luminosity (how bright it is). This breakthrough allowed Harlow Shapley and Edwin Hubble to determine the distances to stars, measure the size of the Milky Way, and confirm the existence of galaxies outside our Milky Way. Leavitt continued to work at HCO until his death from cancer on December 12, 1921, at only 53 years old.
