Every 20 minutes on most nights in the 1950s, two telescopes in the New Mexico desert, weather permitting, took pictures of the sky. Standing 80 miles apart, the telescopes were equipped with fish-eye lenses, allowing them to photograph a 52-degree span—much wider than conventional lenses were capable of. When the Harvard-Smithsonian Meteor Study shoot ended in the late 1950s, thousands of pictures had documented that wedge of the universe.
More than 40 years later, North Carolina astronomers Bob Hayward and Mike Castelaz of the Pisgah Astronomical Research Institute (PARI) began examining the first 100 of the 40,000 images in the New Mexico archive when they discovered something unexpected on one of the film negatives. "We saw a star that may have just exploded," Castelaz recalls.
Novae, formed by a nuclear explosion on the surface of a white dwarf star, are common. About 100 occur in the Milky Way galaxy each year. However, these days it is less common that an astronomer would consult the original glass plates to pinpoint the moment of a nova's inception nearly a half-century ago.
About 3 million of these images—shot on film or photographic emulsion on plates of glass slightly smaller than an iPad—have been taken worldwide over the past 130 years. Supplemented by data logs and observer notes, these images can be used as evidence to challenge or verify the scientific record. They can help astronomers track the orbits of asteroids, the chemical composition of comets and the life cycles of stars—essentially weaving a narrative of the universe.
Yet these photos are endangered. Universities and observatories are running out of space, and to make room for a lab or an office, the plates, some of which are 19th-century daguerrotypes, have been stashed under desks, stacked in closets, stored in flood-prone basements and, in the worst cases, tossed in the trash.
The Apollo missions, space shuttles and interstellar exploration: Astronomy is about the cutting-edge, the Next Big Idea. Within the small astronomy community, only a handful of people—and fewer funding dollars—are devoted to a project as seemingly routine as preserving and digitizing what amounts to a vast photo album.
But it's a vital photo album. The physical object contains an inherent value, longevity and emotional component that the digital does not. Now astronomers shoot only digitally, presenting significant archival and preservation challenges that are different from their analog counterparts.
"We can never go back in time and take the images again," says Castelaz, science director at PARI. "The night sky is always changing, even over a few days."
Thousands of these glass plates reside, waiting to be digitized, at PARI. Located at a former NASA facility that later became a U.S. Department of Defense satellite-tracking post, it is tucked into 350,000 acres of mountain wilderness northwest of Rosman, N.C.
Here you can see vestiges of late '60s Cold War paranoia: A dank, quarter-mile tunnel, better described as a chute, connects two largely windowless buildings. Forty-five years ago, trees were strategically planted in uniform rows to allow military police to patrol the property. Now wild turkeys roost in the branches. A satellite dish near the entrance is emblazoned with a smiley face. Defense Department employees, rightfully suspecting that Soviet satellites were photographing the compound, painted it.
Today the facility is as public as its predecessors were secretive. On this afternoon, dozens of gifted high school students huddled over laptops analyzing digitized versions of these old photos. With an annual $1 million budget funded by PARI president Don Cline, grants and donations, the nonprofit educational and research facility offers tours, "dark sky" nights, science camps and other public programs.
Down the hall, 69-year-old astrophysicist Thurburn Barker donned a pair of white gloves before gently placing a glass-plate photograph on a light table. Through a microscope, the untrained eye sees black blobs surrounded by specks, as if the glass were peppered with flea dirt. But Barker sees two intersecting galaxies, NGC2207 and IC2163, and hovering above them, a nova. That image is from 1975. A year later, the same spot appeared blank. The nova, having expelled its outer shell, had dimmed. (See photo, this page.)
"Within the astronomical community there is an understanding that these are valuable for not only historic purposes, but modern usage," says Barker, director of PARI's Astronomical Photographic Data Archive. "As astrophysics progresses, people may look at objects they have seen before but they didn't know the significance at the time. Now they can dig deeper into the universe."
In November 2007, astronomers from Europe, the U.S. and Canada converged on PARI to discuss the preservation of historic astrophotographic plates. "There was an agreement that there's a problem," Barker says, "because of finances and storage and the changes from film to digital. What came out was that PARI could be designated as a national repository of photographic plates."
PARI has amassed more than 140,000 plates of stars, planets, comets, asteroids, satellites and other celestial bodies taken in North and South America since the late 1800s. In a climate-controlled room, tall metal cabinets are filled with neatly filed photographs that are protected in manila envelopes. These photos were shot at observatories throughout North and South America and had been housed at 16 universities, including the University of Texas, Vanderbilt and Case Western, which donated them to PARI because they had no further use for them.
PARI's initial batch of plates came from University of Michigan research scientist emeritus Nancy Houk, who in 2004 donated her collection to PARI. Castelaz and Hayward drove a U-Haul more than 600 miles to Ann Arbor and brought back 30 boxes containing 3,000 pictures.
Word traveled in the astronomy community that PARI was accepting orphaned photos, and they arrived—by the truckload: 1,300 plates of asteroids, a trove of pictures from the 1973 Skylab complete with NASA documentation. And the collection keeps growing: Last year, PARI traveled to the U.S. Naval Observatory in Virginia to pick up 35,000 plates the federal government no longer wants.
"If we lost all these plates, we'd have just 20 years of history, when we began using digital cameras," Barker says. "That's not enough."