During her days at Swarthmore College, Charlotte Moore found out two things: she was really good at mathematics, and she didn’t like teaching. Those realizations led to a long career in astronomy and physics.

Moore was born 125 years ago yesterday, in Pennsylvania. Her parents were teachers, and they encouraged her to get a good education. She earned a degree in math from Swarthmore. She worked as a substitute teacher to pay her way, but she didn’t like the experience.

Moore got a job at Princeton as a “computer” — she did the tedious calculations that today are done by electronic computers. She worked for Henry Norris Russell, a leading astronomer. They published many papers on binary stars and the chemistry of the stars.

In 1931, Moore moved to Mount Wilson Observatory in California. She studied the Sun — especially sunspots. She came up with the first good idea of the temperatures of the dark blotches, which are much cooler than the surrounding gas. While in California, she also earned her PhD, in astronomy.

Moore later returned to Princeton, where she worked with Norris. She married a fellow scientist, Bancroft Sitterley. And she developed reference tables for the chemical elements that are still in use today.

Charlotte Moore Sitterley finished her career at the National Bureau of Standards. Yet she continued to work for decades after retiring — all the way up to her death, at age 91.

Script by Damond Benningfield