Henrietta S. Leavitt

Henrietta studied at Radcliffe College – the women’s college at Harvard– from 1888 to 1892. She was especially interested in astronomy, the science of stars and space. In 1893, she began working as a volunteer at the Harvard College Observatory to learn more about astronomy, working with Edward C. Pickering. There, she looked at glass photographs of the night sky to measure the brightness of stars and find ones that changed brightness over time, called variable stars.

In 1902 she was offered a full time position at the Harvard College Observatory to research the variable stars in a nearby galaxy called the Small Magellanic Cloud. While studying this group of stars she discovered something amazing. She found that some stars, called Cepheid variables, got brighter and dimmer in a pattern. The longer it took them to change brightness, the brighter they were. This connection between brightness and the time it takes to change is called the Leavitt Law, or the period-luminosity relationship. It gave astronomers a new way to measure the distance to faraway stars and galaxies.

In 1907, she published a paper about over 1,700 variable stars, which established her as a leading expert in the field. In 1912, she published her big discovery about Cepheid variables and how it could help measure distances to far away objects in space.

While at the Observatory, she also worked on creating a system to measure how bright stars appear in the sky, even those far from the North Star (Polaris). In 1909, she wrote about this system in an article called Standard Photographic Magnitudes.

Henrietta Leavitt died of stomach cancer in 1921, at the age of 53. She is buried in Cambridge, Massachusetts. Even though she didn’t always get credit during her lifetime, her work changed the way we understand the universe.