Science

Cecilia Payne’s role in star physics research

www.socialistworld.net, 07/07/2003
website of the committee for a workers' international, CWI

Cecilia Payne, working in the 1920s, was the first person to show how the mechanics of Einstein’s energy conversion formula (e = mc² ) applied beyond our planet - that the process we now call nuclear fusion powered not only our Sun but also the billions of stars in the Universe.

Roy Farrar

A FEW weeks ago an article in the socialist recalled the discovery of the structure of DNA. Francis Crick and James Watson took all the credit, not even acknowledging the ground-breaking work undertaken by Rosalind Franklin, without which they could not have reached their conclusions. This was not the only time female scientists have been ignored, especially when they have made breakthroughs against the orthodoxy of the male hierarchy. ROY FARRAR discusses Cecilia Payne’s role in researching the physics of stars. CWI online.

"There’s a woman out there asking questions!"

She broke new scientific ground by pointing out in her PhD dissertation that ionised hydrogen - not ionised iron - made up over 90% of the Sun’s matter.

Darwin, and geologists working around the same time, had shown how the age of the Earth must be many millions of years old. Prior to the discovery of what we now call radioactivity in the 1890s, scientists were unable to explain how the Sun could have warmed our planet over such a length of time. The fuels known about until then were just not adequate, even given the massive size of the Sun.

Heavy metals

Astronomers looked for the existence of uranium or similar heavy metals breaking down - decaying in accordance with Einstein’s formula - that could release the enormous quantity of nuclear energy that could sustain the Sun over such ’deep time’.

The spectrum lines of the Sun’s radiation were examined (see box) but astronomers did not find the signals for uranium or thorium or any of the heavy, unstable, radioactive metals. Their readings seemed to show the existence of iron, in a gaseous or ionised state.

The Sun’s spectrum
All chemical elements give off distinctive visual signals at certain temperatures. A simple prism can split up the rays of visible light from the Sun into a spectrum of colours.
These are known as the seven colours of the rainbow. (Actually there are only six - when Isaac Newton conducted his first experiments with prisms to describe the nature of light he noted six, he added the seventh later to fit in with his belief in alchemy).
The spectrum lines of the Sun’s radiation were examined using instruments called spectroscopes.

By 1909 it was concluded that the Sun consisted of 66% iron. Iron has the most stable atomic nucleus of all the elements. There all research became bogged down.

Cecilia’s enthusiasm for knowledge and her critical attitude was not welcomed when she went to Cambridge University in 1919. When she went to spend her first night at the university’s telescopic observatory, the night assistant: "Fled down the stairs gasping: ’There’s a woman out there asking questions.’"

But Arthur Eddington, who had provided experimental proof of Einstein’s theory of gravitational, or general, relativity, was pleased to take on Payne as a tutorial student. Eddington first assigned Payne to the problem of the Sun’s interior.

But a woman, no matter how capable, even with Eddington’s backing, could not work in this subject in England. In 1923 she moved to Harvard, Massachusetts.

Payne’s thesis adviser, also director of the Harvard University Observatory, kept her away from the new electronic equipment. When she taught courses, they were never listed in any Harvard catalogue. Her salary was classified as ’equipment expenses’.

It wasn’t just an environment which belittled women’s ability to do scientific research. Payne wrote of her first experiences at Harvard: "I expressed to a friend that I liked one of the other girls in the house where I lived at Radcliffe College. She was shocked: ’But she’s a Jew!’ was her comment. This frankly puzzled me... I found the same attitude towards those of African descent."

In 1923 if one referred to a computer, this meant not a machine but a person who could perform the elaborate calculations required in scientific work.

Payne found at Harvard this meant backrooms where many "slump-shouldered spinsters" calculated star locations or tabulated results of experiments. Getting married, or complaining of the low pay, meant they faced the sack!

Payne refused to be pushed into their ranks and conducted research which showed the role of hydrogen in the energy of the Sun (see box).

The "magic furnace"
In her dissertation Stellar Atmospheres, A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars, Cecilia Payne pointed out that ionised hydrogen - not ionised iron - made up over 90% of the Sun’s matter.
She argued, correctly, that the previous interpretations of stellar observations did not take into account the effects of differing amounts of ionisation of the various elements due to different temperatures in the layers of the Sun’s interior.
The latest research in Europe at the time gave support to the concept of how hydrogen, under tremendous temperatures and pressures, could actually be transformed into helium and at the same time releasing sufficient energy for the Sun’s "magic furnace".

But Dr Henry Norris Russell had published an earlier paper showing the abundance of iron in the Sun. He refused to acknowledge that a mistake had been made.

Russell and the old guard just said the hydrogen wasn’t there. Their positions and professorships, their research and papers, their standing and reputations, meant that Payne must be wrong.

Russell was a bully and self important and he had influence - most of the grants and appointments on the East Coast of the USA were by his say so.

The astronomer Edward Milne tried to intervene but lacked Russell’s power. Payne was forced to recant and insert into her original dissertation: "The enormous abundance [of hydrogen]... is almost certainly not real."

Russell and his circle were eventually proved wrong but she never received a real apology. History was then re-written, claiming that Russell and co had known about the presence of the abundance of hydrogen all along!

Years later it was recognised that Payne’s PhD dissertation was the best in 20th century astronomy. In 1977, a couple of years before she died, she received a prestigious award from the American Astronomical Society.

In her acceptance speech and memorial lecture for the prize, ironically the Henry Norris Russell Prize, she said:

"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; it engenders what Thomas Huxley called the Divine Dipsomania.

"The reward of the old scientist is the sense of having seen a vague sketch grow into a masterly landscape. Not a finished picture, of course; a picture that is still growing in scope and detail with the application of new techniques and new skills.

"The old scientist cannot claim that the masterpiece is his own work. He may have roughed out part of the design, laid on a few strokes, but he has learned to accept the discoveries of others with the same delight that he experienced his own when he was young."