Up until 1925, the scientific consensus was that the Sun had a similar chemical composition to Earth.
Then, one Ph.D thesis changed all that.
This is Cecilia Payne. She discovered that the Sun was mainly composed of hydrogen.
Cecilia Payne was born in England in 1900. A the age of 19, while at Newham College, Cambridge, she attended a lecture by Sir Arthur Eddington. The lecture was about something scientifically very important. It was about how Eddington demonstrated that Einstein was right.
Payne was hooked and realized then that she wanted to study physics and, in particular, astronomy:
The result was a complete transformation of my world picture. When I returned to my room I found that I could write down the lecture word for word.
So, following the lecture, she switched her studies to focus on astronomy.
After completing her studies (for which she wasn’t awarded a degree – Cambridge didn’t award degrees to women back then) she left England in 1923 to join the new graduate program in astronomy at Harvard College Observatory.
At the time, Harvard had the world’s largest collection of spectra of stars. The light of a star is split into its constituent colours and recorded on photographic plates. When you do this, dark lines appear in the rainbow of colours. You’ll something a bit like this (but the patterns would be far more complex for a star):
By comparing laboratory spectra against stellar spectra, it is possible to determine all the chemical elements that exist in the Sun and other stars. See Finding Out What a Star Is Made Of With Spectroscopy for more details. This had already been done and catalogued by the time Payne arrived at Harvard – it was well known that the Sun contained hydrogen, helium, oxygen, carbon and many other elements.
What Payne did with this catalogued data was revolutionary. She examined the properties of the spectral lines, and with her newly acquired knowledge of quantum physics, she was able to determine the relative abundances of the 18 elements found a typical spectrum. Within 2 years of arriving at Harvard she had produced a thesis for her doctoral degree: she showed that the majority of stars are made of the same stuff, and in the same quantities.
She also calculated that hydrogen and helium make up 98% of a the matter in a typical star. Most of the mass of a star is accounted for by the two lightest elements! And this extrapolates, by the way: most of the mass of the visible Universe is hydrogen.
Harlow Shapley, the director of the Harvard College Observatory, sent Payne’s thesis to a professor at Princeton who replied that the result was “clearly impossible”. Payne, worried about her scientific reputation and future career, amended her thesis to include a statement that her calculated abundances of hydrogen and helium were “almost certainly not real.”.
Within a few years, however, she was found to be correct. Not only did we now know that all stars are essentially the same, her work also allowed astronomers to determine the temperature of any star from its spectrum. This is how we know that, say, Sirius has a surface temperature of about 10000 K and that Betelgeuse has a surface temperature of about 3250 K.
So, why hasn’t everyone heard of Cecilia Payne?
I’ve been studying astronomy for a few years now. I only heard about Cecilia Payne a few weeks ago. Thinking that I must have just missed something, I searched through all the Open University PDFs for my physics and astronomy courses for the word “Payne”. Nothing.
And @PenguinGalaxy has previously told me that there is no mention of Payne in her astronomy text books either.
I have just asked Twitter too. A friend (that studied star formation during her masters degree!) had never heard of her either. One person (from Australia) did know of her from university physics textbooks.
My point is… why isn’t she as famous as, say, Hubble. She should be. What she discovered was amazing and changed how we see the Universe.
This clearly is not right.
Why isn’t there a space telescope named after Cecilia Payne?
We have various space telescopes named after scientists. Examples include Hubble, Fermi, Kepler, Newton and Spitzer.
NASA have missed a few opportunities to name a space telescope after Payne. It would have been apt to name one of the space telescopes currently observing the Sun (like Solar Dynamics Observatory) after her. Or perhaps one of the telescopes mapping hydrogen in the Universe.
But it’s not too late! How about one of the upcoming Solar Space Telescopes? Come on ESA, how about naming your upcoming Solar Orbiter space telescope after Cecilia Payne-Gaposchkin? She is from Europe after all!
Cecilia Payne, on accepting the Henry Norris Russell Prize from the American Astronomical Society
I thought I’d end this post with a quote from Cecilia Payne:
The reward of the young scientist is the emotional thrill of being the first person in the history of the world to see something or to understand something. Nothing can compare with that experience… The reward of the old scientist is the sense of having seen a vague sketch grow into a masterly landscape.
I have written a few posts about Spectroscopy if you want to learn more about this fascinating subject.
Update: On August 23rd 2013, Who Made Your Pants launched a new pair of pants named after Cecilia Payne. Here is Stuart Clark’s Guardian article about it: Pants named after astronomer Cecilia Payne-Gaposchkin.Follow @kashfarooq