One of the great things about the history of science is the discovery of a great but hidden story. Unlike art, or writing, or other things that make us human, most of the amazing discoveries of science are hidden from view. Instead, we get a “smoothed out” version taught in school and in various popular accounts.

How do we know what stars are made of? To answer that question, I could write about Fraunhofer lines, spectrographs, maybe even mention the discovery of the expansion of the universe. But there’s a hidden story here, the story of a scientist named Cecilia Payne.

Astronomy was one of the few fields in which women were early on encouraged to participate. Of course, “participate” is a relative thing. Mostly women were used as “computers,” performing long and complex calculations so that the male astronomers could theorize, get published, and earn tenure. But a few women overcame the barriers and found their own way.

Cecilia Payne was from England, but came to Harvard University to study the spectra of stars – mostly because Cambridge University in England did not award degrees to women. Unbelievably, this was less than 100 years ago, In 1923, Payne began her studies at Harvard.

At the time, most scientists believed, based on what they saw in the spectra of stars, that stars were made mostly of iron. Payne had another idea. Despite what everyone else thought, Payne analyzed the spectra of stars and thought she saw the overwhelming signature of hydrogen and helium, the two simplest and lightest elements in the universe.

Payne’s advisor, the famous astronomer Henry Norris Russell (of the Hertzsprung-Russell diagram) , convinced Payne to remove her most spectacular finding – the abundance of hydrogen and helium – from her Ph.D. thesis. It was simply too controversial, and Payne acquiesced.

A few years later, Russell recognized his mistake. Payne had seen what no one else had. Stars were mostly made of the universe’s very simplest ingredients.

Why was this so important? Simply this – stars are the places where all the complex elements of the universe are formed. Everything around us – carbon in our toast, oxygen in our air, silicon in our computers – was formed long ago and far away inside giant stars. There are other wonderful hidden stories behind these discoveries, too. But our awakening to this amazing fact started with Cecilia Payne, a woman scientists who overcame the obstacles to see where no one else had seen before. She looked inside the rainbows of the stars, and discovered there one of the best-hidden secrets of the universe.