Tracking the paths of the “Starlight Detectives” at Science on Saturday
When astronomer Isaac Roberts showed a photograph of the Andromeda Nebula to the Royal Astronomical Society, it caused a huge sensation. “There were audible gasps in the audience,” astronomer Alan Hirshfeld told the audience at the first Ronald E. Hatcher Science on Saturday lecture at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory on Jan. 9.
“The professional astronomers had never seen such a clear image of the nebula,” Hirshfeld said.
The year was 1888 and such photographs were unheard of. But Roberts was one of many “starlight detectives,” who pioneered the use of cameras and spectroscopy along with powerful telescopes to see space more clearly than it was ever possible with merely the naked eye, Hirshfeld said. These early discoveries led to our modern concepts of what the universe outside our galaxy looks like and the origins of the universe.
Hirshfeld, a professor of physics at the University of Massachusetts-Dartmouth and an associate of the Harvard College Observatory, traced the origins of modern astronomy and the precursors of powerful telescopes like the Giant Magellan Telescope in Chile, a massive 80-foot diameter device that will be completed in 2021. The lecture was based on his book, “Starlight Detectives: How Astronomers, Inventors, and Eccentrics Discovered the Modern Universe,” (New York Literary Press, 2014).
The first tool astronomers used was their own eyes, Hirshfeld said. “The human eye is a horrible astronomical instrument but it was all we had for hundreds of years,” he said.
Galileo Galilei revolutionized astronomy in the 16th century by giving astronomers a much better view of the solar system with his development of some of the earliest telescopes. Two hundred years later, telescopes were getting bigger and better but were still limited by what the human eye could see, Hirshfeld said.
Revolutionizing astronomers’ toolkit
The next revolution in the astronomer’s toolkit came with the development of the camera and “that is where the trail of the starlight detectives takes off,” Hirshfeld said.
The first working photographic process developed by Louis Daguerre, and introduced as the daguerreotype in 1839, swept through the world, Hirshfeld said. He added that it is hard to imagine today how a photograph of the moon caused such a sensation when it was displayed at the World Exposition in London. But photography was a relatively new art at the time and people had never seen such a thing. “People were astounded at having the moon,” Hirshfeld said. “It inspired people.”
It took a few decades for astronomers to use photography, and it was amateur astronomers who ventured into this area. Andrew Ainslie Common, an English sanitary engineer, began attaching a camera to his telescope in the 1880s. When he took a photo of the Orion Nebula, it was perhaps the first time a camera captured objects in space not visible to the human eye.
Common set up his telescope in the backyard of his home outside London, but at some point, astronomers realized that a mountaintop observatory would capture better images. Common eventually sold his reflector to British politician Edward Crossley who gave it to the Lick Observatory in Mountainside, California, Hirshfeld told the crowd
When the Lick Observatory, the world’s first modern mountaintop observatory, began operating in 1888, scientists observed spiral nebulae that changed their concept of the universe, Hirshfeld said. Until then, scientists believed the universe was empty outside of our galaxy. But with clearer photos, astronomer James Keeler estimated there were many thousands of unrecorded nebulae in the sky. (Scientists now believe there are more than 1 million). That observation meant that the universe was anything but empty.
The invention that made astronomy high-tech
But what propelled astronomy into “a modern high-tech science,” Hirshfeld said, was the development of the first spectroscope in the 1860s by Robert Bunsen, a German chemist who invented the Bunsen burner, along with physicist Gustav Kirchhoff. The two were the first to devise an instrument that could identify elements by the colors or spectra of the light waves coming from the elements.
Hirshfeld demonstrated how the spectroscope works by passing out small diffraction grating lenses. The lens looks like a photographic slide but it acts like a prism to disperse light from different elements into its component wavelengths, with different elements breaking down into different colors.
The spectroscope allowed scientists to analyze the elements of the sun and other objects in space. It led to the discovery by William and Margaret Huggins in the 1860s that the stars are composed of the same elements found on earth.
When Edwin Hubble arrived at the Mount Wilson Observatory in Pasadena, California, in 1919, he was able to use the Hooker Telescope, a 100-inch telescope that was the world’s largest telescope at the time, as well as photography and spectroscopy.
Hubble’s research showed that the Andromeda Nebula was too distant to be part of the galaxy and was actually another galaxy, proving that there is a universe beyond the Milky Way. “It really solidified the idea that we live in a universe of galaxies,” Hirshfeld said. Hubble truly revolutionized astronomy when he found that the farther apart galaxies are from each other, the faster they move away from each other, Hirshfeld said. He put forth the concept that the universe began with a single burst of energy and has been expanding ever since, which formed the basis for the Big Bang Theory. Astronomy “became a cutting edge science” in the 1920s “largely due to the unheralded role of the starlight detectives,” Hirshfeld concluded.
The Science on Saturday crowd gave Hirshfeld a warm round of applause. Among them was Alan Lapinsky, a physics teacher at Princeton Day School, who said he would use some of the information in his own classes. “It was an interesting talk,” he said. “I always learn new things I can cover in my classes.”
John Weaver, a seventh grader at Lawrence Middle School, was equally enthusiastic. “I found it super interesting,” he said. “I learned a lot about the past of space exploration.”
“You always learn something astounding,” said Carol Wintermute, who has been coming to the lectures for the past few years with two friends from the Princeton Windrows retirement community in Princeton. “You get hooked. You really do.”
Shirley Tilghman will be Jan. 16 lecturer
The next lecture on Jan. 16 is by molecular biologist and former Princeton University President Shirley Tilghman. She will discuss “The Wild and Wacky World of Epigenetics,” which involves the study of how external factors can regulate how genes switch on and off.
The free lectures are held each Saturday through March 12 at 9:30 a.m. at PPPL, 100 Stellarator Road, Princeton. Doors open at 8:15 a.m. with refreshments for early birds. Plan to come early to the lecture because seats fill up quickly.
If Science on Saturday is canceled due to inclement weather or other emergency, a message will be left on the Science on Saturday Hotline at (609) 243-2121.
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