Overlooked No More: Henrietta Leavitt, Who Unraveled Mysteries of the Stars

This article is part of Overlooked, a series of obituaries about remarkable people whose deaths, beginning in 1851, went unreported in The Times.

In the early 20th century, when Henrietta Leavitt began studying photographs of distant stars at the Harvard College Observatory, astronomers had no idea how big the universe was. Debate raged over whether all of the objects visible through the telescopes of the day were within our own Milky Way galaxy, or whether other galaxies — or “island universes,” as they were then called — might exist somewhere out in space.

Leavitt, working as a poorly paid member of a team of mostly women who cataloged data for the scientists at the observatory, found a way to peer out into the great unknown and measure it.

What’s now commonly called Leavitt’s Law is still taught in college astronomy courses. It underpinned the research of other pioneering astronomers, including Edwin Hubble and Harlow Shapley, whose work in the years after World War I demolished long-held ideas about our solar system’s place in the cosmos. Leavitt’s Law has been used on the Hubble Telescope and the James Webb Space Telescope in making new calculations about the rate of expansion of the universe and the proximity of stars billions of light years from earth.

“All of those major discoveries rested on Leavitt’s discovery,” Wendy L. Freedman, a professor of astronomy and astrophysics at the University of Chicago, said in a phone interview, referring to the explosion of knowledge about space over the last century. “It’s the bedrock foundation of so much of what we do today in cosmology and astrophysics in general.”