The picture on the left is in the Public Domain. Henrietta Swan Leavitt (1868-1921). The asteroid 5383 Leavitt and the crater Leavitt on the Moon are named after her. Leavitt attended Oberlin and Radcliffe where she experienced hearing loss. At Radcliffe, she took an astronomy class and pursued more classes upon graduation. She worked at the Harvard College Observatory, one of "Pickering's computer women" to help map the stars using photographic plates.
She was promoted to the photometry department and used photographic techniques to determine star magnitudes. The staff began with the "North Star Sequence" as a standard from which 46 stars were selected to study. They applied this scale to measure thousands of stars where Leavitt discovered 2,400 variable stars, asteroids, and other heavenly objects.
In 1908, Leavitt discovered the period-luminosity law that enabled astronomers to estimate the distance from the earth to stars based on their brightness. This discovery allowed astronomers to estimate greater distances up to ten million light-years away, much greater than one hundred light-years. Hubble used the law to estimate the distance of the Andromeda galaxy in light-years.
She contributed to studies of variable stars in the Magellanic Clouds., including finding 25 Cepheids in the dwarf galaxy, the Lesser Magellanic Cloud. Of the 2400 variable stars she discovered, 1,777 of them are in the Magellanic Clouds. She was nominated for the Nobel Prize in physics, but she had already passed away 4 years earlier.