Monday, February 18, 2013

Annie Jump Cannon and the Spectra of Stars

I got the idea for this piece from a blog by Astroian (Ian Cohen) and then did my own research.  Annie Jump Cannon is familiar to many astronomers through the Harvard Classification Scheme for stars that she invented: O, B, A, F, G, K, M.  Also, her name comes up every year when the AAS award named for her is given out.  It is for a woman scientist within 5 years receipt of her PhD for "distinguished contributions to astronomy".

Annie has an interesting life story.  She was born in 1863, the daughter of a shipbuilder father and astronomy-loving mother.  She went to university to study math and physics and unfortunately contracted scarlet fever while an undergraduate at Wellesley and became partially deaf.

It was hard as a woman to become an astronomer in the late 1800's, but she had the diligence to search for opportunities and the good fortune to be taken in by Sarah Whiting, a Professor of Physics and Astronomy at Wellesley.  Through her help, Annie was able to work part time as Dr. Whiting's assistant and later pursue graduate studies.  I don't believe she received a PhD at that time, although was later (1925) awarded an honorary PhD from Oxford, the first awarded by Oxford to a woman.

In the late 1890's Annie was hired as an assistant by Edward Pickering at Harvard.  She became a member of the "Pickering women" group to produce the Henry Draper Catalog (funded by the Draper family) of stars and stellar spectra.  The pay was low, less than that earned by the secretaries, but the work was grand.  She did an enormous amount of observing to make the catalog.  During the catalog production a disagreement broke out over how to classify the stars.  Annie as able to find an elegant solution that was a compromise between the factions, resulting in the OBAFGKM scheme.  It divided stars into spectral classes based on the strength of their Balmer absorption lines.  She eventually became the William C. Bond Astronomer at Harvard and was awarded the Henry Draper medal of the NAS.  She died in 1941.

Annie Jump Cannon was a pioneer in astronomy in the early 1900's.  Her work and splendid example helped pave the way for future women to gain acceptance as astronomers.