Cecilia Payne’s Discovery of Hydrogen in Stars

By Yashika Sharma

December 14, 2022
astronomer Cecilia Payne Gaposchkin using a telescope
Cecilia Payne Gaposchkin. Credits: Astronomical Society of the Pacific, courtesy AIP Emilio Segrè Visual Archives, Physics Today Collection

Stars have adorned the night sky since the dawn of time. 

But a crucial question about stars “what are stars made of?”, had always excited the astronomers of early times. 

It was believed that the stars have a similar elemental composition to that of Earth but it’s not that.

Stars are mainly composed of 2 elements hydrogen and helium and traces of other elements. 

Back to the question, the answer to this crucial question was given by Cecilia Payne Gaposchkin, an American Astronomer and Astrophysicist. 

Cecilia Payne was a pioneering Astrophysicist who made groundbreaking discoveries about the composition of stars.

The composition of stars was described by Payne in her doctoral thesis in 1925.

Cecilia Payne’s Thesis on Stellar Composition

In the early 1930s, she began working at the Harvard college observatory as a college student, where she studied the spectra of stars.

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This was the time when she made one of the most significant contributions to understanding the stellar universe.

 In 1925 she published her doctoral thesis titled “Stellar Atmospheres: A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars.” 

Payne was able to precisely relate the spectral classes of stars to their actual temperatures by applying Meghnad Saha’s ionization theory.

She showed that the variation in stellar absorption lines was due to different amounts of ionization at different temperatures. 

She discovered that silicon, carbon, and other major metals detected in the Sun’s spectrum were present in roughly the same proportional amounts as they are on Earth (around 2%)1.

However, in her investigation, she also found that stars are primarily composed of hydrogen and helium, which was contrary to the scientific beliefs of that time. 

Criticisms of Payne’s Thesis By the Scientific Community

When Payne’s thesis was reviewed, American astronomer Henry Norris Russel, who stood by the theory of American physicist Henry Rowland, stated that Payne’s observations can’t be true.

He discouraged her from concluding that stars are predominantly composed of hydrogen as it was contrary to the scientific consensus that the Earth and the Sun had identical elemental composition.

In response to these criticisms and the growing anxiety of getting her results published, she downcased her own findings and said that her conclusion might be a possible error2.

A few years later Russel stated the same thing as Payne, he realized she was right about the results when they derived the same results by different means.

In 1929, he published his own paper about the composition of stars with a brief mention of Cecilia Payne.

Flash forward, to a few years later another astronomer Otto Struve described Payne’s doctoral thesis as the most brilliant thesis in the field of astronomy.

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Russel was credited for the explanation for the composition of stars for several decades.

And Payne’s contribution was hidden from the world for a very long time. 

Impact of Cecilia Payne’s Discoveries on Astronomy

Before Payne’s discovery, it was widely believed that the composition of stars was similar to that of Earth.

This belief was based on the fact that the light from stars had a similar spectrum to that of Earth, and it was thought that this indicated that the stars were made up of the same elements as Earth.

However, Payne’s research showed that this was not the case and that stars are actually mostly composed of hydrogen and helium, with only trace amounts of other elements.

This discovery was groundbreaking because it challenged the prevailing beliefs of the time and provided a new and more accurate understanding of the composition of stars.

It also had far-reaching implications for our understanding of the universe and the elements that make up stars and planets.

Payne’s discovery helped to lay the foundation for the modern study of astrophysics, which is the scientific study of the physical properties and behavior of celestial objects and phenomena.

This field of study has contributed greatly to our understanding of the universe, including the origins and evolution of the universe, the formation and behavior of stars and galaxies, and the nature of black holes and other exotic objects.

Additionally, Payne’s discovery played a key role in establishing astrophysics as a separate discipline from astronomy.

Prior to her work, astrophysics was not considered a distinct field of study, but rather a subfield of astronomy.

However, Payne’s research helped to establish astrophysics as a separate discipline, with its own distinct theories, methods, and body of knowledge.

Today, astrophysics is a highly respected and influential field of study, Cecilia Payne eventually won over all her critics and her work continues to be highly regarded and is widely recognized.

Cecilia Payne-Gaposchkin’s Biography

Early Life of Cecilia Payne 

Cecilia was born on May 10, 1900, in Wendover, England to a family of intellectuals; her father was a London barrister, historian, and pianist. 

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Her primary schooling was done in Wendover at a private school, and her later education was done at st. Paul’s Girls school. 

In 1919, she won a scholarship that covered all her expenses at Newnham College, Cambridge University.

In college, she studied botany, physics, and chemistry but she dropped out of botany in her first year. 

She wasn’t awarded a degree as Cambridge didn’t award degrees to women.

Payne realized that there was no hope for her scientific interests if she stayed in the UK.

She moved to the United States in 1923 and became the first person to earn a doctorate in astronomy and got her Ph.D. in 1925 from Radcliffe College, Harvard University. 

Cecilia Payne Accomplishments

Her discoveries and expertise were recognized with numerous prizes and honors.

  • In 1934, she was awarded the Annie Cannon Award in Astronomy, she was the first recipient of this award.
  • She was awarded the Henry Norris Russel prize by the American Astronomical Society in 1976, one of the most prestigious awards in the field of astronomy.
  • She was awarded the Rittenhouse medal from the Rittenhouse Astronomical Society at the Franklin Institute in 1961. 
  • The asteroid 2039 discovered by astronomers in 1974 at Harvard College observatory was named after Cecilia Payne Gaposchkin – 2039 Payne-Gaposchkin.

Difficulties Cecilia Payne Faced in Her Career 

Cecilia Payne Gaposchkin’s scientific journey was not easy at all, despite doing all the duties of a professor she was not given a professorship during her tenure at Harvard University.

She was titled technical assistant to professor Shapley, all of this only because she was a woman.

Although she was considered one of the most brilliant astronomers of the 20th century she was never elected to the elite National Academy of Sciences.

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As the times were changing she was offered a full-time professorship and the chairperson of the astronomy department at Harvard in 1956.

She became the first woman to be recognized at Harvard University.

Later Life and Legacy

After publishing her thesis, Payne continued to conduct research and make important contributions to astronomy and astrophysics.

She was an inspiration to many because of the path she forged into the predominantly male-dominated scientific field.

Cecilia was a brilliant astronomer; her discovery completely revolutionized the understanding of astronomy at the time.

Because of her excellence, many fields developed within astronomy and it embarked on the birth of astrophysics.

She was presented with numerous challenges throughout her academic career.

Despite these challenges, she was adamant about continuing in science since she was driven by a burning desire to learn more about the universe.

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Cecilia Payne Gaposchkin died on 7 December 1979 in Cambridge, Massachusetts.

Today, Payne is remembered as one of the most important figures in the history of astrophysics.

She was an inspiration to many women in science and her legacy is continued to be celebrated by our scientific community.

There is no joy more intense than that of coming upon a fact that cannot be understood in terms of currently accepted ideas.

Cecilia Payne, American astronomer

Recommendations

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References

  1. Devesh Sharma, Pranav Mahapatra, and Vikrant Singh, ‘What is a Star & How Do Stars Work?‘, Evincism, May 15, 2021, “We can refer to these stars as huge hot balls of hydrogen, helium, and other elements as well”, https://evincism.com/how-do-stars-work/[]
  2. Cecilia Payne and the Composition of the Stars‘, American museum of natural history, n.d, “To protect her career, Payne inserted a statement in her thesis that the calculated abundances of hydrogen and helium were almost certainly not real”, https://www.amnh.org/learn-teach/curriculum-collections/cosmic-horizons-book/cecilia-payne-profile[]
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