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Henrietta Leavitt discovered more than 2,400 variable stars while working at the Harvard College Observatory. Despite being deaf and the era's prejudices against women, which prevented Leavitt at first from being paid and later pursing her own topics of study, she developed the Harvard Standard of photographic measurements.
Leavitt was born on July 4, 1868 in Lancaster, Massachusetts. She studied astronomy in 1892, during her final year of college. The following year she began unpaid work as a volunteer at the Harvard College Observatory. Her first job was as a "computer" measuring and counting stars in photographic plates. Seven years later she became a paid employee earning $10.50 per week.
Unable to use telescopes because she was a woman, Leavitt used photographic plates to measure the magnitude of variable stars. (Variable stars have a change in apparent magnitude as seen from the Earth caused by swelling and shrinking, or light being blocked from reaching the Earth. Cepheid variable stars are very luminous.)
In 1908, some of Leavitt's findings related to her study of variable stars in images of the Magellanic Clouds were published in the Annals of the Astronomical Observatory of Harvard College:
- Brighter variable stars appeared to have longer periods
- Stronger stars appeared to have slower cycles
- The cycles of variable stars depend on how bright they really are (intrinsic luminosity)
- Cepheid variable stars in the Small Magellanic Cloud are all about the same distance from the Earth
- A period-luminosity ratio could be used to measure the distance from Earth to any Cepheid star
Leavitt developed a standard of photographic measurements called the Harvard Standard that was accepted by the International Committee of Photographic Magnitudes. She used hundreds of photographic plates and logarithmic equations to order stars according to magnitudes of brightness.
Others used Leavitt's formula to further their own studies:
- Ejnar Hertzsprung plotted the distance of stars
- Harlow Shapley measured the size of the Milky Way
- Edwin Hubble ascertained the age of the Universe
Hubble said Leavitt deserved a Nobel Prize for her work; she died of cancer on December 21, 1921 before she could be nominated. A colleague considered her "the brightest woman at Harvard." An asteroid and a crater on the moon have been named for her.
Resources:
CWP - Henrietta Swan Leavitt
MIT - Henrietta Leavitt (1868-1921)
She is an Astronomer - Henrietta Leavitt (1868-1921)
Wikipedia - Henrietta Swan Leavitt
Wikipedia - Variable star
The Woman Astronomer - Henrietta Swan Leavitt - Lady of Luminosity
http://www.physics.ucla.edu/~cwp/Phase2/Leavitt,_Henrietta_Swan@871234567.html
http://www.aas.org/cswa/status/2005/JANUARY2005/HenriettaLeavitt.html [image 1]
http://ottawa-rasc.ca/features/marchHubble/leavitt-graph.gif [image 2]
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Re: Henrietta Leavitt: "The Brightest Woman at Harvard"
