This collection explores the discoveries and methods of American astronomer Henrietta Swan Leavitt.  She worked at the Harvard College Observatory (HCO) as a “computer”, examining glass photographic plates in order to measure and catalog the brightness of stars. This work led her to discover the relationship between the luminosity (brightness) and the period of brightening/dimming of Cepheid variables (stars that have a distinct brightness and dimming period). Her discovery provided astronomers with the first “standard candle” with which to measure the distance to faraway galaxies and paved the way for modern astronomy's understanding of the structure and size of the universe.  

Follow the steps throughout the collection to determine the ways that  Leavitt and the other Harvard Computers identified variable stars. In these resources, you'll find images of glass plate photographs that the Computers used for their calculations, as well as videos, quiz questions, and images of Henrietta Leavitt. For more information about Leavitt's life, view the information tab on the first three resources. 

For more web resources, check out our other collection: Henrietta Swan Leavitt Web Resources. 

Keywords: Harvard Computers, astronomy, female astronomers, history of science, women in STEM, Project PHaEDRA, John G. Wolbach Library, Center for Astrophysics