Ada Lovelace and Henrietta Swan Leavitt, of computers and stars

Ada Lovelace (1815-1852), was the first person to write a computer program (calculating Bernoulli numbers) for the Analytical Engine. She wrote about the potential uses of computers and software, even though they had not been invented yet. Ada Lovelace Day is celebrated on the 24th of March by bloggers to promote the achievements of women in science and technology.

The story of Ada Lovelace reminded me of Henrietta Swan Leavitt (1868 - 1921). Soon after she finished her bachelor's degree, she was employed at the Harvard College Observatory as a "human computer" of sorts. This was not an unheard of thing for the time, as women in science were often relegated to the "menial" tasks. Specifically her job was to examine the photographic plates taken by the telescope, and measure and catalog the brightness of the stars.

Henrietta Swan Leavitt (1868 - 1921)

While studying the photographic plates, she noticed that some of the brighter variable stars (stars whose apparent brightness as seen from Earth changes over time) appeared to have longer periods. With further study, she confirmed that there was a relationship between the luminosity and period of these stars (called Cepheid variables) and published her findings in the Annals of the Astronomical Observatory of Harvard College. This information proved to be a key for astronomers to be able to measure distances across the universe - this research proved particularly important for Edwin Hubble's work.

Cepheid variables in galaxy M100

Eventually she was made head of stellar photometry, and continued her work off and on while battling illness, until her death in 1921.  She was almost nominated for a Nobel Prize in Physics for her work, but unfortunately died before she could be (the Nobel is not awarded posthumously).  The asteroid 5383 Leavitt and the crater Leavitt on the Moon are named in her honor.

If you would like to learn more about Henrietta Swan Leavitt, you may be interested in the book, Miss Leavitt's Stars: The Untold Story of the Woman Who Discovered How to Measure the Universe

For more info about Ada Lovelace Day, and to read more blog posts celebrating women in science and technology, head over to Ada Lovelace Day homepage

References and photos from:
http://findingada.com
http://en.wikipedia.org/wiki/Henrietta_Swan_Leavitt
http://hubblesite.org