Henrietta Swan Leavitt was born July 4th, 1868 to George Roswell Leavitt and Henrietta Swan Kendrick. When she was 20 years old she enrolled in the Society for Collegiate Instruction of Women, now Radcliffe College, the female annex of Harvard. Leavitt became interested in astronomy after taking a course during her senior year. After graduating in 1892, she volunteered as a “computer” at the Harvard College Observatory. There she examined tiny stars in photographs of the night sky and recorded the data she collected in ledger books. She then became an assistant in studying variable stars, stars that pulse intermittent or regular pattern over a period of time. In 1902, Leavitt was made a permanent member of the observatory. Leavitt discovered 2,400 variable stars, which accounted for about half of the variable stars known during her time. In 1912, she figured out how to measure a star's size and then calculate its distance from Earth. This allowed scientists to measure stars that were millions of lightyears away. Leavitt remained working at the observatory until her death on December 12, 1921.
The Harvard College Observatory (HCO) was established in 1839. During the late 1800’s, E.C. Pickering developed the HCO into a major research center where Cepheid stars were studied. Harvard College Observatory is home to the largest collection of stellar glass plate negatives -an astounding 500,000- dating back to the mid 1800’s.