Henrietta Swan Leavitt (July 4 1868 – December 12 1921) was an American astronomer, as well as being the deaf daughter of a Congregational church minister [http://www.csmonitor.com/2005/0705/p15s01-bogn.html. She was born in Lancaster, Massachusetts to an old Massachusetts Puritan family which had settled in the Massachusetts Bay Colony in the early part of the seventeenth century.

Leavitt began work in 1893 at Harvard College Observatory as one of the women "computers" brought in by Edward Charles Pickering to measure and catalog the brightness of stars in the observatory's photographic plate collection. She noted thousands of variable stars in images of the Magellanic Clouds. In 1908 she published her results in the Annals of the Astronomical Observatory of Harvard College, noting that a few of the variables showed a pattern: brighter ones appeared to have longer periods. After further study, she confirmed in 1912 that the variable stars, actually Cepheid variables, of greater intrinsic luminosity indeed had longer periods, with a fairly close and predictable relation between the two.

This relationship provided an important yardstick for measuring distances in the Universe, if it could be calibrated. One year after Leavitt reported her results, Ejnar Hertzsprung determined the distance of several Cepheids in the Milky Way, and with this calibration the distance to any Cepheid could be determined. When Cepheids were detected in other galaxies such as the Andromeda Galaxy, the distance to those galaxies could also be determined. These distances settled the debate on whether the galaxies were external to the Milky Way or part of it.

Leavitt worked sporadically during her time at Harvard, often sidelined by health problems and family obligations. But by 1921, when Harlow Shapley took over as director of the observatory, she was head of stellar photometry. She succumbed to cancer by the end of that year.

Awards and honors

• The asteroid 5383 Leavitt and the Leavitt crater on the Moon are named in her honour.
• Four years after her death, the Swedish mathematician Gösta Mittag-Leffler considered nominating her for the Nobel prize. The nomination was based on her work formulating the relationship between periodicity and luminosity of Cepheid variables. However, as she was already dead, she was never nominated.

Reference

1868 births | 1921 deaths | American astronomers | Women astronomers | Christians in science

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