Though he lived in Paris, he traveled across Europe and Asia in search of optimal vantage points for observing the night sky. Janssen dove eagerly into this new form of light analysis. New elements are showing up right and left because you have this new tool.” “All of a sudden there’s this almost magical technique by which you can know the elements of these distant bodies. “Before the spectroscope you had no idea what the sun was made of, or what stars are made of,” says Deborah Warner, a curator in the division of medicine and science at the National Museum of American History. “This provides a sort of ‘fingerprint’ which can confirm the presence of that chemical.”īy analyzing the emission spectra of specific elements in the lab, then turning their spectroscopes on the stars, researchers could make out the chemical composition of everything from our sun to the stars across the galaxy.Ī spectroscope designed to look at the sun. “The two scientists found that every chemical element produces a unique spectrum,” the American Institute of Physics writes. Similarly, the dark lines that Fraunhofer had discovered represented light being absorbed by a cooler element at the surface of the sun. For example, hydrogen burns orange, but when observed through a spectroscope, it becomes clear that the orange is made up of multiple individual narrow wavelengths of light. The scientists determined that the bright lines appeared when a hot gas was burned. In 1859, Bunsen and Kirchoff discovered that heating different elements produced bright lines of light in the spectroscope-and those lines of light sometimes corresponded to the dark Fraunhofer lines. That knowledge would come several decades later, with German researchers Gustav Kirchhoff and Robert Bunsen. These black lines were named for Fraunhofer, even though he didn’t understand what they were. An early model had allowed physicist Joseph Fraunhofer to observe the sun in the early 1800s, but he was puzzled by black lines interrupting the normal colors. Similar in design to a telescope, the spectroscope worked like a super-powered prism, dispersing light into measurable wavelengths. A new instrument called a spectroscope was upending the field of astronomy. The mid-1800s was an exciting time to peer at the heavens. At the time, though, Janssen didn’t know what he’d seen-just that it was something new. He became the first person to observe helium, an element never before seen on Earth, in the solar spectrum. On August 18, 1868, Janssen managed to do just that. Armed with the latest technology of the day and observations made by other Western astrophysicists, Janssen was determined to pry open the secrets of the galaxy.
Just one more step and the chemical composition of the universe will be revealed,” wrote astrophysicist Pierre Jules César Janssen to his wife from an observatory in Italy in December 1862.
“I have obtained one of the finest and least expected results-Spectra of the stars!-and beautiful spectra with colors and magnificent lines.