Celestial Events

Natural History, July, 1999 by Richard Panek

Twice this century, scientists working at the same research center made entirely serendipitous discoveries that changed astronomy forever.

In the early 1930s, Karl G. Jansky, a young Bell Labs radio engineer, went searching for the source of interference that had been plaguing transatlantic telephone service. At the Holmdel, New Jersey, facility, he constructed an aerial antenna array that measured thirteen feet high and one hundred feet long, attached it to four wheels from a Model T Ford mounted on a circular track, and set the entire contraption rotating.

Jansky could easily attribute two types of noise to local and distant weather patterns. The source of a third, however, proved more elusive. From charts that translated the noise into ink graphs, he concluded that the heaviest concentration of "weak, hiss-type static" traveled a full circuit of the sky in twenty-three hours, fifty-six minutes--or precisely the length of a sidereal day (the time it takes the stars to complete one revolution in the heavens). This peak signal seemed to be emanating from the vicinity of the constellation Sagittarius, toward the center of the Milky Way galaxy.

The source, Jansky concluded, was the stars, which would explain why the noise never went away: the stars themselves never really go away.

This was the first time ever that a "telescope" had picked up radio signals from space, and Jansky's discovery made the front page of the New York Times. The National Broadcasting Corporation (NBC) invited him to hook up a connection from Holmdel to a Manhattan radio studio and broadcast his "star noise" to the nation, an act of celestial eavesdropping he soon repeated for a lecture audience at the American Museum of Natural History. But after that first burst of attention to his research, Jansky transferred to another Bell Labs facility and apparently took public and scientific curiosity about radio astronomy with him.

It wasn't until after World War II that astronomers began to understand how Jansky had opened a vital new window on the universe: we could now see all the wavelengths along the electromagnetic spectrum that fall outside the narrow band to which our eyes happen to be sensitive. And, unlike scientists working with optical telescopes, astronomers working in infrared, ultraviolet, gamma, or X rays can retrieve data whenever they want. Over the past half-century those wavelengths have revealed a universe of previously unimaginable violence: pulsars, quasars, black holes, and, just recently, hypernovas (single bursts that pack as much energy into one explosion as ten thousand suns release in their entire lifetimes).

In the early 1960s, history repeated itself in Holmdel when a pair of Bell Labs radio engineers working on a twenty-foot horn antenna for the Echo communications satellite picked up some noise they couldn't explain. Arno Penzias and Robert Wilson tried eliminating all possibilities for the disturbances, including scrubbing the antenna clean of something they termed "a white dielectric substance" (a.k.a. pigeon droppings), but the hiss persisted.

Meanwhile, researchers from nearby Princeton University, had begun to make some predictions about the Big Bang, at that time still a highly controversial hypothesis. If the Big Bang actually did happen, they reasoned, the universe would still be resonating with energy at the lowest extreme of the electromagnetic spectrum. When the Princeton crew found out what was happening at Bell Labs, they rushed over and confirmed that the radio measurements corresponded to their predictions.

Jansky's antenna array disappeared long ago, but Penzias and Wilson's horn antenna (the two scientists shared a Nobel Prize in physics for their discovery) remains, apparently in working order. During a recent visit, Wilson looked around the shed that used to serve as his workstation and commented that the equipment there cost $25,000 in 1962. "Now," he sighed, "all this could be done with a couple of PCs."

Last year Bell Labs unveiled a sculpture, in the approximate shape and at the approximate location of Jansky's merry-go-round array, on what is now an island of grass near the parking lot at the main Holmdel facility. The sculpture's antenna is aligned as the original was on the tenth of September 1932, at 7:10 P.M.--the only day for which the data from Jansky's pioneering work survive.

About a mile away, at the Bell Labs Crawford Hill facility, a plaque designates the horn antenna as a National Historic Landmark "confirming the Big Bang theory of the creation of the universe, forever changing the science of cosmology."

To find the bright spot Jansky "saw" in the Milky Way, locate Sagittarius, the archer (or the teapot). In the northern latitudes it's a summer constellation, hugging the southern horizon. (It will appear due south at midnight in early July and at about 9 P.M. by late August.)

And to see what Penzias and Wilson "saw," find ... anything. It doesn't even need to be something in the sky. If everything in the universe was present at the beginning and has been expanding outward ever since, then the Big Bang is, in a sense, evident everywhere all the time. So, wherever you are, at any time of the day or night, you can take a look around and know: you're doing astronomy.