Star Stuff

Star Stuff

By Shawn Radcliffe

Cecilia Payne-Gaposchkin on the Mystery of Stars

“We're made of star stuff. We are a way for the cosmos to know itself,” American astronomer and science communicator Carl Sagan said in his 1980 television series Cosmos. This quote remains one of the most widely repeated celebrations of human existence, soothing that uneasy feeling of insignificance we often have when contemplating our place in a universe that is so much larger than any one of us.

In a way, Sagan’s quote illuminates our very nature — a fitting phrase, because the elements (or “star stuff”) that combine to give us substance are the same elements that burn at the heart of stars.

English-American astronomer and astrophysicist Cecilia Payne-Gaposchkin described this link between stars and ourselves in a radio talk she gave in November 1925 as part of a series about astronomy by the Harvard College Observatory:

“In the spectrum of the Sun, we can pick out all the two thousand colors that are given out by an atom of iron; they are exactly the same as the colors that would be given out by a piece of iron, heated in the electric arc in the laboratory. A common chemistry and a common physics run through the universe.”

At the time, scientists still had much to learn about stars, including the reactions that occur within that allow them to give off light and heat.

The radio broadcast, with talks by 25-year-old Payne and other scientists, was published the following year as The Universe of Stars: Radio Talks from the Harvard College Observatory. It provides a glimpse into Payne’s role in advancing our understanding of the nature of stars, and in doing so, gives us a glimpse at our own stellar nature.

Although we know stars best as the hundreds of points of light that appear in the night sky — along with our own sun, which somehow seems to stand out from the rest — Payne shows listeners that stars are much more than specks of light above us:

“When we look at the twinkling light of the stars, we need all our powers of imagination to visualize what they really are. Every one of those points of light is actually a huge mass, often far larger than the Sun. Every one shines because it is hot — so hot that it glows by its own light.
[…]
When you look at the night sky, you are looking at an almost inconceivably great quantity of matter; and therefore when I talk about the stuff the stars are made of I am telling you what we know of the Chemistry of the Universe."

This commonality among stars — and between stars and all matter on Earth — was a new idea at the time. Payne continued to work throughout her life to increase our understanding of the interconnectedness of all these pieces of the universe.

Our understanding of stars is limited by how we are able to study them. Unlike matter on the Earth that we can collect in a jar and experiment on or analyze directly, we only know stars by what they share with us — heat, light, and other electromagnetic radiation. Some of that light, though, has taken thousands of years to reach us, which puts our “vast” solar system in perspective. As Payne describes it:

“Overhead we shall see thousands of twinkling points of light that we call the stars. Although light takes a third of a day to cross the solar system, the light that reaches us from the Milky Way may have been travelling five thousand years.”

However, the light that reaches us from stars is more than just discarded energy and photons. If you look at our own sun, its “waste products” provide the heat and light that sustains life on earth — and allows us to exist long enough to ponder the nature of the sun and other stars.

Stars also provide countless moments of inspiration and wonder to anyone gazing up at them at night — whether that means wondering about the mysteries that continue to stream forth from their illuminated interiors or contemplating your own stellar nature. As Payne puts it:

“[Stars] are all pouring out light into space and we can catch that light as it strikes the Earth, and analyze it. In a fundamental sense, that light was once as much a part of the stars as clay is a part of the Earth. Light is a form of energy, and it is the energy of a star that makes it shine, and keeps it going, and enables it to survive. A star literally lives on its light.”


Cecilia Helena Payne-Gaposchkin (1900–1979) was a British-born American astronomer and astrophysicist who proposed in her 1925 doctoral thesis that stars were composed primarily of hydrogen and helium.

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