If I said the word computer, almost everyone would know exactly what I was talking about and probably how to use one, but I bet you didn’t know that the term was around long before the machine and that a group of “computers” revolutionized modern astrophysics.
Edward Charles Pickering was the director of the Harvard Observatory for almost 50 years and against popular consensus of the day decided to hire women to work for him, which total unheard of in academia at the time. Fed up with incompetent male assistants and knowing that a woman could be paid vastly less than a man (a sad fact the still reverberates through history to this day), he declare to the university that “Even my maid could do a better job” and that is exactly what he did. In 1885 he hire his maid, Williamina Fleming to process astronomical data that was piling up at the observatory and in 1886 after the university received a large grant, Pickering hired more women to aid his research.
So why did we start his article talking about computers? Well amongst the halls of Harvard this is exactly what this group of women were referred as, ‘Pickering’s Computers’. The term computer is a lot older than you think, originating in France around 1645 literally means, ‘One who calculates’. They we also derogatorily called ‘Pickering Harem’, another sad testament of the time. The group quickly grew to 16 in number and amazingly processed and categorised more than 10,000,000 stars. Of this group there were 3 women in particular that changed the face of astrophysics.
The first was Annie Jump Cannon, who personally classified more than 500,000 stars and actually invented the method of spectral classes that we assigned to each star by looking at their Balmer absorption lines. Her classification system contained 7 primary categories; O, B, A, F, G, K & M and 10 sub categories that were numbered from 0 to 9. Amazingly she could categorize 3 stars per minute just by glancing at their spectral lines using a magnifying glass, which was about 16 times faster than her male counterparts from other universities. On May 9, 1922 a full 24 years after its creation, the international Astronomical union passed the resolution to formally adopt her classification system, which is still being used to this day.
Another amazing woman from this group was Henrietta Swan Leavitt. Pickering assigned her the task of cataloguing and categorising ‘variable stars’ whose luminosity varies over time but he would never have thought that she would make a discovery of the magnitude that she did. Leavitt discovered that all of the Cepheids within each Magellanic Cloud were at approximately the same distances from the earth, so that their intrinsic brightness could be deduced from their apparent brightness and from the distance to each of the clouds. “Since the variables are probably at nearly the same distance from the Earth, their periods are apparently associated with their actual emission of light, as determined by their mass, density, and surface brightness.” Her discovery is known as the “period-luminosity relationship” and it is still being used by astronomers today to measure the distances to the stars and the size of the cosmos itself.
The last stand out woman of Pickering’s group was Cecilia Payne. Cecilia was the first woman in history (or more appropriately herstory) to become a professor at Harvard University and laid the ground work for modern astrophysics. Payne studied stars of high luminosity in order to understand the structure of the Milky Way. Later she surveyed all the stars brighter than the tenth magnitude. She then studied variable stars, making over 1,250,000 observations with her assistants. This work later was extended to the Magellanic Clouds, adding a further 2,000,000 observations of variable stars. Payne was able to accurately relate the spectral classes of stars to their actual temperatures by applying the ionization theory. She showed that the great variation in stellar absorption lines was due to differing amounts of ionization at different temperatures, not to different amounts of elements. She found that silicon, carbon, and other common metals seen in the Sun’s spectrum were present in about the same relative amounts as on Earth, in agreement with the accepted belief of the time, which held that the stars had approximately the same elemental composition as the Earth. However, she found that helium and particularly hydrogen were vastly more abundant. Initially shunned by the scientific community her work was later accepted and became the basis for modern astrophysics.
We salute you wonderful ladies and thank you for your amazing dedication and commitment to science, despite the hardships and sexist behaviours of the day. Science is a machine of knowledge and each contribution is a cog towards the future of human kind, these 3 ladies represent large meaningful cogs in the science machine and we would hate to think where we would be without their wonderful contributions. Hats off people, you’re reading about scientific royalty.
Stay Curious – C.Costigan
