Henrietta Levitt was the first person to discover the scientific importance of a star’s brightness—so why has no one heard of her? Learn all about a female pioneer of astronomy in this picture book biography.

Henrietta Swan Leavitt was born on July 4, 1868, and she changed the course of astronomy when she was just twenty-five years old. Henrietta spent years measuring star positions and sizes from photographs taken by the telescope at the Harvard College Observatory, where she worked. After Henrietta observed that certain stars had a fixed pattern to their changes, her discovery made it possible for astronomers to measure greater and greater distances—leading to our present understanding of the vast size of the universe.