Henrietta Swan Leavitt explained to kids

Henrietta Swan Leavitt was an American astronomer. She worked at the Harvard College Observatory in the early 1900s. Leavitt's work helped astronomers understand how to measure the distances to stars and galaxies. Leavitt was born in 1868 in Massachusetts. She went to college at Wesleyan College in Georgia. After college, she worked as a teacher for a few years. Then she went back to school to study astronomy. Leavitt began working at the Harvard College Observatory in 1892. She was part of a team of women "human computers" who were hired to study and catalog the stars. The women examined photographic plates of the night sky to look for stars that changed in brightness. Leavitt noticed that some stars changed in brightness in a regular pattern. She discovered that these stars were actually pulsating, or expanding and contracting. Leavitt realized that the period of a star's pulsation was related to its luminosity, or brightness. Leavitt's discovery allowed astronomers to measure the distances to stars and galaxies. Before her discovery, astronomers could only estimate the distances to stars. But Leavitt's work showed them how to make more accurate measurements. Leavitt died in 1921, at the age of 53. Today, she is considered one of the most important astronomers of the 20th century.