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For thousands of years, stars have served as tools for navigation, inspiration for myths, and sources of wonder. But in 1925, a groundbreaking discovery by a graduate student named Cecilia Payne revealed the true nature of the shimmering points of light in the sky.
After earning her doctorate in 1925, Cecilia Payne dedicated her entire academic career to Harvard. As a woman, she was barred from becoming a professor, and so she spent many years in low-paid research jobs despite her overwhelmingly successful thesis.
Payne was a prodigious young scientist whose innovative thinking at the age of 24 reshaped how the universe was understood. Her work challenged long-established ideas and became a crucial step in astrophysical research.
In 1956, Payne finally broke new ground at Harvard by becoming the university’s first female professor and the first woman to chair a department. Previously, the first woman to be admitted into Harvard’s faculty was Alice Hamilton in 1919, but she only ever retained a role as an assistant professor.
While many scientists of the era believed that stars (including our very own Sun) were made of heavy metals similar to the Earth, Payne believed that they had a different chemical makeup altogether. She posited that hydrogen and helium were the primary elements found in stars. But how did she go about proving this?
Like any scientific hypothesis that went against the dogma of the time, Payne’s research faced significant skepticism. But as a young woman in the male-dominated field of astronomy, she felt those tensions even more.
In the 1600s, humanity began constructing telescopes that allowed humans to observe stars more closely. As a result, many observations were made about these points of light, including that they tended to cluster together into cloudlike “nebulas.”
By the 1800s, people started using prisms in a process known as spectroscopy, which spreads incoming sunlight into a rainbow of colors. Later, astronomers placed these prisms into telescopes in the hope of recording and analyzing starlight.
The 19th-century invention of spectroscopy enabled scientists to break starlight into distinct colors that would then interact with a photographic glass plate coated in an emulsion. When photons of light touched the emulsion, dark marks would appear. These would basically be the signatures of far-away stars.
By placing prisms in telescopes, astronomers revealed patterns that hinted at the chemical makeup of stars, though many still believed they shared Earth’s elemental composition.
Payne utilized these up-to-date advancements in atomic physics to analyze starlight. She connected the behavior of electrons in atoms to the spectral lines observed in stars, which provided a clearer picture of their chemical and physical processes.
Payne rejected her mentor’s suggestions to replicate earlier work and instead analyzed decades of untouched spectroscopic data. At the time, no other institute in the world had as many emulsion plates as Harvard, all of which preserved star signatures.
In the 1800s, scientists assumed that stars contained the same materials as Earth because of similarities in spectral patterns on emulsion plates. This belief remained unchallenged until Payne’s work demonstrated the overwhelming abundance of hydrogen and helium in stars.
Payne’s interest in astronomy ignited after attending Arthur Eddington’s lecture in 1919, where he verified Einstein’s then brand-new theory of general relativity using solar eclipse data. The images he captured of the stars seemed to show their positions shift in the sky, since the Sun’s gravity was pulling on their starlight and altering their pathways.
Initially, Payne studied botany, but quickly switched over to physics in her first year. Her education in atomic physics was brought about by Ernest Rutherford (who discovered that every atom has a positively charged nucleus) and Niels Bohr (who explored the behavior of electrons orbiting that nucleus).
After being denied full academic opportunities in England, Payne moved to the United States in 1923. She began her graduate studies at Harvard College Observatory, one of the few institutions that welcomed women in astronomy, where she made her revolutionary discovery.
At Harvard, most women in astronomy were relegated to roles as "computers," performing calculations and analyzing starlight. Payne broke this mold by pursuing independent research, advancing beyond the constraints placed on her female colleagues.
By the time Payne started conducting research at Harvard, scientists had already figured out the source of the patterns seen on spectroscopy plates. They were attributed to the shifting energy levels of electrons as they spun around an atom’s nucleus and emitted or absorbed light.
Payne integrated the insights of Indian physicist Meghnad Saha (pictured) into the behavior of gases under extreme conditions, enabling her to calculate how temperatures and pressures in stars can affect spectral patterns.
By analyzing starlight spectra from the surface of stars, Payne identified blank regions where gases like hydrogen and helium absorbed light. This helped her calculate the abundance of elements in stars and finally reveal their true and overwhelming composition.
Payne’s research demonstrated that hydrogen and helium are far more abundant in stars than any heavier element. This finding challenged previous beliefs and reshaped scientists’ understanding of the chemical makeup of the universe.
Payne’s work revealed how the extreme pressures and temperatures within stars influence their light patterns. She ultimately completed her thesis in 1925, and she earned her doctoral degree in astronomy in the process.
During Payne’s time, there were many challenges that scientists (especially women) faced whenever they disputed scientific dogma. Despite the brilliance of her thesis, Payne faced strong criticism, particularly from Henry Norris Russell, a prominent astronomer who doubted her findings.
Payne’s journey is a reminder of the human effort behind science. Her curiosity, courage, and intellect illustrate how a single inquisitive mind can transform our understanding of the natural world and humanity’s place within the cosmos.
Sources: (National Geographic) (Britannica) (American Museum of Natural History) (American Physical Society)
See also: 30 space terms for understanding the universe better
Through her research, Payne paved the way for scientists to understand not only how stars evolve (from their formation to their explosive deaths or quiet fades), but also how their energy is transferred through their outer layers.
Born in Wendover, England, on May 10, 1900, Cecilia Payne pursued her passion for science and music in her teen years before earning a scholarship to attend Newnham College at the University of Cambridge in 1919.
Payne’s 200-page thesis is still regarded as a masterpiece of astronomical research. Its precision, attention to detail, and transformative conclusions have inspired generations of scientists to explore the stars with greater understanding.
Just four years after Payne’s thesis, Henry Norris Russell confirmed her conclusions, validating her claims about the elemental composition of stars. This acknowledgment cemented her work as a cornerstone of modern astrophysics.
Interestingly, the color of light always corresponds to a specific atom. For example, carbon atoms would always emit or absorb the same amount of light as each other, while it would differ to the atoms of other elements.
For thousands of years, humanity has gazed up at the stars in fascination, using them to navigate vast oceans, mark the passage of seasons, and inspire myths, art, and poetry. These celestial lights, scattered across the night sky, seemed mysterious yet constant, their true nature beyond comprehension. Many scientists and astronomers spent much time theorizing about the nature of these far-flung objects, and the early 1900s saw many of these theories debunked by a brilliant young graduate student.
What beliefs did scientists have about the stars a century ago? What are these celestial objects truly made of? And how did a 24-year-old would-be astronomer reveal the secrets of starlight? Click through this gallery to find out.
What are stars really made of?
The story of how a grad student changed our understanding of the universe
LIFESTYLE Astronomy
For thousands of years, humanity has gazed up at the stars in fascination, using them to navigate vast oceans, mark the passage of seasons, and inspire myths, art, and poetry. These celestial lights, scattered across the night sky, seemed mysterious yet constant, their true nature beyond comprehension. Many scientists and astronomers spent much time theorizing about the nature of these far-flung objects, and the early 1900s saw many of these theories debunked by a brilliant young graduate student.
What beliefs did scientists have about the stars a century ago? What are these celestial objects truly made of? And how did a 24-year-old would-be astronomer reveal the secrets of starlight? Click through this gallery to find out.