Today, ask any astronomer what the Sun and other stars are made of, and you'll be told, "Hydrogen and helium and trace amounts of other elements". We know this through a study of sunlight, using a technique called "spectroscopy". Essentially, it dissects sunlight into its component wavelengths called a spectrum. Specific characteristics in the spectrum tell astronomers what elements exist in the Sun's atmosphere. We see hydrogen, helium, silicon, plus carbon, and other common metals in stars and nebulae throughout the universe. We have this knowledge thanks to the pioneering work done by Dr. Cecelia Payne-Gaposchkin throughout her career.
The Woman Who Explained the Sun and Stars
In 1925, astronomy student Cecelia Payne turned in her doctoral thesis on the topic of stellar atmospheres. One of her most important findings was that the Sun is very rich in hydrogen and helium, more so than astronomers thought. Based on that, she concluded that hydrogen is THE major constituent of all stars, making hydrogen the most abundant element in the universe.
It makes sense, since the Sun and other stars fuse hydrogen in their cores to create heavier elements. As they age, stars also fuse those heavier elements to make more complex ones. This process of stellar nucleosynthesis is what populates the universe with many of the elements heavier than hydrogen and helium. It's also an important part of the evolution of stars, which Cecelia sought to understand.
The idea that stars are made mostly of hydrogen seems like a very obvious thing to astronomers today, but for its time, Dr. Payne's idea was startling. One of her advisors - Henry Norris Russell - disagreed with it and demanded she take it out of her thesis defense. Later, he decided it was a great idea, published it on his own, and got the credit for the discovery. She continued to work at Harvard, but for time, because she was a woman, she received very low pay and the classes she taught weren't even recognized in the course catalogs at the time.
In recent decades, the credit for her discovery and subsequent work has been restored to Dr. Payne-Gaposchkin. She is also credited with establishing that stars can be classified by their temperatures, and published more than 150 papers on stellar atmospheres, stellar spectra. She also worked with her husband, Serge I. Gaposchkin, on variable stars. She published five books, and won a number of awards. She spent her entire research career at Harvard College Observatory, eventually becoming the first woman to chair a department at Harvard. Despite successes that would have gained male astronomers at the time incredible praise and honors, she faced gender discrimination throughout much of her life. Nonetheless, she is now celebrated as a brilliant and original thinker for her contributions that changed our understanding of how stars work.
As one of the first of a group of female astronomers at Harvard, Cecelia Payne-Gaposchkin blazed a trail for women in astronomy that many cite as their own inspiration to study the stars. In 2000, a special centenary celebration of her life and science at Harvard drew astronomers from around the world to discuss her life and findings and how they changed the face of astronomy. Largely due to her work and example, as well as the example of women who were inspired by her courage and intellect, the role of women in astronomy is slowly improving, as more select it as a profession.
A Portrait of the Scientist Throughout her Life
Dr. Payne-Gaposchkin was born as Cecelia Helena Payne in England on May 10, 1900. She got interested in astronomy after hearing Sir Arthur Eddington describe his experiences on an eclipse expedition in 1919. She then studied astronomy, but because she was female, she was refused a degree from Cambridge. She left England for the United States, where she studied astronomy and got her PhD from Radcliffe College (which is now a part of Harvard University).
After she received her doctorate, Dr. Payne went on to study a number of different types of stars, particularly the very brightest "high luminosity" stars. Her main interest was to understand the stellar structure of the Milky Way, and she ultimately studied variable stars in our galaxy and the nearby Magellanic Clouds. Her data played a large role in determining the ways that stars are born, live, and die.
Cecelia Payne married fellow astronomer Serge Gaposchkin in 1934 and they worked together on variable stars and other targets throughout their lives. They had three children. Dr. Payne-Gaposchkin continued teaching at Harvard until 1966, and continued her research into stars with the Smithsonian Astrophysical Observatory (headquartered at Harvard's Center for Astrophysics. She died in 1979.