Wednesday, 13 January 2010

A different sort of sine qua non: Cecilia Payne-Gaposchkin

My post yesterday was about devoted supporters of astronomers, who had a quiet role in an astronomer's discovery or at any rate their ability and inspiration. This morning I was goaded by Marcus Chown - who I couldn't possibly ignore! - into writing about an astronomer herself. She's one I've already written about on the Galaxy Zoo Forum and for She is an Astronomer; this is a copy of the latter, which was written back in October. Marcus Chown tweeted: "My mission in life is to get Cecilia Payne Gaposhkin the recognition she deserves!" And she certainly deserves a lot more than she ever had. So she can go here, too.

Cecilia Payne as pictured on She is an Astronomer.

The Feature of this weekend is the story of one of my favourite historical astronomers, Cecilia Payne-Gaposchkin, who is profiled in on our main page here.

I first read about her quite by accident. She made a crucial discovery about the Sun and all stars, which paved the way to realising how stars burn: that they, unlike the Earth, are made mostly of hydrogen. The experts on stars in her day did not believe her until other scientists began to turn up the same results. This was nothing unusual in her life: she studied at Cambridge but could not earn a degree, because they were not given to women; and the same thing happened in America when she completed her doctorate a few years later. Yet she was never put off, and made huge contributions to astronomy throughout her life. Karen Masters, who heads Galaxy Zoo's "She is an Astronomer" project, wrote this for me:

Her career was littered with small frustrations even given her early seminal work (for which any man would have been feted), but she never seemed to think it mattered. She is quoted as saying: "I simply went on plodding, rewarded by the beauty of the scenery towards an unexpected goal."

I first found out about her whilst reading Arthur Miller's "Empire of the Stars", a biography of Chandrasekhar and the long-disbelieved concepts of black holes, and about fights and put-downs between scientists who, he says, "find themselves in thrall to their intellectual endeavours with a degree of intensity and competitiveness that can exact a high psychological toll . . . [so] sometimes act and react in ways which may seem inexplicable to lesser human beings." That's another story. Although this biography states how unkind and sometimes dishonest Eddington could be to other scientists, he was kind to young Cecilia, an undergraduate at Cambridge starting in 1919:

. . . Cecilia Payne recalled how rude the eminent physicist Ernest Rutherford was to her. He often began his lectures, in which she was usually the sole woman in the audience, by looking her straight in the eye and uttering the word, "Ladies", followed by a long pause, ". . . and gentlemen." Rutherford's daughter, Eileen, a friend of hers, told Payne that Rutherford . . . had said to her, "She isn't interested in you, my dear. She's just interested in me." Payne was so offended that she gave up physics and switched to astronomy, a field that had attracted her ever since hearing Eddington lecture. Eddington immediately set her a problem on the structure of stars and was very helpful to her.

I felt like going back in time and telling her not to bother about such pettishness, until I recalled that Rutherford would probably have been the man who, effectively, decided her future - and would not see her scientific ability as a reason to allow her to achieve anything, or even to let her voice be heard. I'm not telling you this to whinge about someting that happened 90-odd years ago, but to show encouragement to anyone who's feeling the same sort of thing now - and, for those who aren't, to show how much things have, on the whole, improved since then.

The Sun, which Cecilia Payne discovered is composed mostly of hydrogen - taken from this interesting link about stars' energy.

Payne's discovery was essentially applying new theories to the Sun's spectrum: its unique signature of light, certain wavelengths of which are dimmed or exaggerated by cool and hot atoms respectively. But this only shows their presence or absence. In 1920, while Payne was still at Cambridge, Megnad Saha worked out how to calculate the abundances of each element, and the theory was completed by Arthur Milne and Ralph Fowler, also at Cambridge.

Payne, later Payne-Gaposchkin when she married, appears on and off in Miller's book. She appears in a similar vein - not an individual story, like Einstein, but a crucial part of so many larger ones - in Marcus Chown's wonderful "The Magic Furnace", where he effectively picks up the next part of her story:

Cecilia Payne had become fascinated by the problem of decoding the message in starlight while still an undergraduate at Cambridge. However, she was forced to go to America to pursue the problem because of the exclusion of women from British astronomy. Payne enrolled for a doctorate at Radcliffe College, which was on the doorstep of Harvard Observatory, the home of the world's richest collection of stellar spectra. She quickly set about applying Milne and Fowler's method to some of the Harvard spectra, obtaining her first results in 1925. Those results contained a bombshell.

Some of the most prominent lines in the solar spectrum were due to the lightest element, hydrogen. This was unexpected, because Payne's calculations indicated that, at the temperature of the sun's surface, only a minuscule fraction of all hydrogen atoms should be in the necessary state to produce hydrogen lines. The only reasonable explanation was that this fraction must still represent a very substantial numbre of atoms. In other words, hydrogen atoms must be extraordinarily abundant on the sun. Similar logic applied to the second lightest element, helium. In fact, Payne's calculations seemed to be implying that the two lightest elements made up an astonishing 98% of the mass of the sun!

This was surprising because astronomers had, for centuries, simply assumed that the Sun was made of iron - even Eddington's bestseller, "The Internal Constitution of the Stars", published in 1926 and still a classic today, makes that assumption. Until the discovery of spectroscopy, scientists had no reason to realise that the proportion of the elements on Earth (i.e. mostly iron, silicon, oxygen, etc.) was any different in the rest of the Universe.

Chown continues:

It was too incredible to be true. In her doctoral thesis, Payne called the result "spurious". She even went so far, in a scientific journal, as to declare, "The abundance of both hydrogen and helium in stars is improbably high and is almost certainly not real." In rejecting what would one day go down as her greatest discovery, Payne was heavily influenced by Henry Norris Russell, the American astronomer who had discovered red giants . . .

Nevertheless, Russell was eventually forced to admit he had made a mistake. By 1929, the evidence for the super-abundance of hydrogen,in particular, was overwhelming . . . A hydrogen sun also resolved a major problem with Eddington's theory [i.e. that an iron sun, to shine as powerfully as the Sun does, would have to be an incredible 40 million degrees in temperature! Eddington, at first, did not believe Payne either.] . . .

The discovery by Payne . . . had implications for beyond the sun . . . [it] . . . indicated that hydrogen and helium were the most common elements in the entire universe.

Not a minor discovery by any means! But because Payne's results were ignored until more came along, from male scientists, she missed her glory. Nevertheless, some of her colleagues did their best to fight or circumvent the system for her. Harlow Shapley, for instance, specially created the Astronomy Department at Radcliffe, because the Physics Department did not allow women to receive PhDs. (The title of her thesis was "Stellar Atmospheres, A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars". Otto Struve said that it was "undoubtedly the most brilliant Ph.D. thesis ever written in astronomy".) Shapley also kept her as a "technical assistant", an underpaid position beyond which women could not rise, though in practice she was a working scientist. She was awarded the title of "Astronomer" in 1938; in 1956 she was finally allowed to be called a "Professor"; and, eventually, was the first woman ever to head the department.

A long struggle, but not unsuccessful, so I write this as a message to all of you not to be put off even if things take a long time! Her later work included: high-luminosity stars and the structure of the Milky Way; and variable stars - cataloguing, with her students, over 1,250,000, and then another 2,000,000 in the Magellanic Clouds.

Mira, a variable star, the yellow star just between the two clumps of trees. This picture is from Astronomy Picture of the Day; go there and you can move your mouse over it to see the diagram.

Karen, mentioned above, found me a lovely blog article about Cecilia Payne-Gaposchkin which is worth a read; and, Googling around, I found parts of her autobiography available to read online (with lengthy introductions from people who knew her; you'll have to scroll down a long way to get to her own words! The book's on my Christmas list though!). Of arriving in America, besides amusing anecdotes about the freer culture she encountered there, and her women friends' amiable mirth over her constrained talk and dress, she writes these beautiful lines:

When I arrived in Cambridge, Massachusetts, I had crossed a gulf wider than the Atlantic Ocean. I had left the world of dreams and stepped into reality. Abstract study was a thing of the past; now I moved among the stars.

Also, you may have been wondering why, since Harvard was such a temple of spectra, an Englishwoman was the one who made use of it. It had long been a place where women could do quite respectable work they enjoyed, and Payne, rather than criticising the culture, simply tells us of its differences in a very wise way:

Miss Cannon [Annie Jump Cannon, who headed the department and left an important legacy] was extraordinarily kind to me. She might well have resented a young and inexperienced student who was preumptuous enough to attempt to interpret the spectra that had been her own reserve for many years. She never gave a sign of doing so. "Do you realise," Shapley later asked me, "how easily Miss Cannon could have chucked a monkey wrench into the works for you?" With my arrogance of youth I had not even thought of it; I had even permitted myself to wonder how anyone who had worked with stellar spectra so long could have refrained from drawing any conclusions from them. She was a pure observer, she did not attempt to interpret. As I look back I see how her work has outlasted my early efforts at interpretation.

The Large Cloud of Magellan, from Astronomy Picture of the Day.

Helen has just started a topic about how to get the IAU resolution - to support and encourage female astronomers - to work. To me, this story seems to be not about methods but people: those who are kind; those who accept others who are different, as well as different scientific approaches (Cecilia Payne herself included); those who take on difficult tasks and are willing to break with tradition; those who expect others to achieve highly and set them challenging things to work on; those who look far. In other words, openness, goodwill, and expectations. That's my take, anyway. Please post your ideas.

P.S. From the Galaxy Zoo post - some stars, posted by Citisue and Sophie.

Credit: Sloan Digital Sky Survey.

Credit: Sloan Digital Sky Survey.

Now who shall I write about?


Debra said...

Thanks for a great article about a great woman astronomer. She does deserve more credit and recognition than she has received.

Clear skies!

Alice said...

Many thanks Debra, and you have a fascinating website!

Sakib said...

I've mentioned this before but I get frustrated at the horrendous lack of attention given to female astronomers (both current and historical ones)! Brilliant article, I'm glad that the prejudice against Cecilia wasn't enough to dissuade her from pursuing her dreams. There was a lot of backlack against Chandrasekhar amongst the at the time elitist scientific fraternity simply because he was Indian! I'm so glad that modern science is all encompassing and doesn't impose barriers against people based on their gender, age or race. None of the stuffy academics from a century ago would have envisioned a global network of international cooperation.
Harlow Shapley is one of my favourite astronomers from the 20th century and it was noble of him to help Cecilia. I have a feeling that if a male astronomer discovered the true composition of the Sun, he would have been widely appplauded and showered with appraisal. The double standards against women at the time (and even now) are just sickening.
Its quite cool to note that certain things we take for granted would have seemed inexplicably unbelievable when they were first discovered, especially when they contradict a deep rooted belief. Obviously right now, the notion of the Sun being made out of iron but it is understandable why this would have been believed at a time in the past.
There is an Armenian female astronomer called Elma Parsamian who has done briliant working regarding young stars and cometary reflection nebulae. Believe it or not she is 80 years old yet she continues in her quest for knowledge of the universe! Now I would say that's dedication!

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