Searching the stars, hoping ET left the lights on

If ET has left a light on in the window, Paul Horowitz hopes to be the first to spot it.

This week, the Harvard University physics professor unveiled a sensitive new telescope, the first to be used exclusively to hunt for light signals from any intelligent extraterrestrials who may lurk in the galaxy.

Scientists have been hunting for ET for at least 45 years using large radio-telescopes. Within the last decade they have expanded the search to include light.

But these efforts have been akin to "looking through soda straws," he says. Telescopes check out individual stars one by one, typically piggybacking with other projects looking at the same patch of sky. The result: Scientists have been able to scan only about one ten-thousandth of the sky.

The telescope, with the largest light-gathering surface east of the Mississippi, is designed to take in the whole sky from its shed at the university's Oak Ridge Observatory in Harvard, Mass.

The project is one small example of SETI's slowly growing respectability as a scientific enterprise. Where scientists once had to beg for time on radio and optical telescopes to conduct the hunt, they now build instruments dedicated to it full time.

The SETI Institute in Mountain View, Calif., for example, plans to flip the switch on 10 of its 30 new radio- telescope dishes at the Allen Telescope Array in Hat Creek, Calif. later this month. By using off-the-shelf equipment to hold down costs, and developing some fancy processing techniques for incoming signals, the Allen Telescope Array team will be able to hunt for radio signals from ET at the same time astronomers use these antennas for more mainstream research.

Although scientists have given these efforts a broad nod through organizations such as the National Research Council, funding still comes largely from private donors. The Allen array is named for Microsoft cofounder Paul Allen, who wrote the check for the observatory's initial installation. The money for Horowitz's telescope came from the Planetary Society in Pasadena, Calif., and a private foundation.

Central New England is not known for boundless numbers of cloudless, haze-free nights each year. But Horowitz says that for the work he and his team do, crystal-clear skies aren't needed. They anticipate that their quarry would make its presence known through extremely bright, if brief, flashes. He notes that Earth technology has generated such signals for several decades. He calculates that the light from pulsed lasers found at federal labs would be more than enough to do the job if it shined backward through a large telescope. Each burst of light would be 10,000 times brighter than the sun in white light.

But the bursts are extremely quick, measured in trillionths of a second. Thus, much of the $350,000 his team has spent on the 72-inch telescope and its domicile has gone into designing and building a camera capable of detecting faint, fast bursts of light across wide swaths of sky.

Horowitz says he expects to begin gathering data in two weeks.

Finding ET is "undoubtedly a long shot," he acknowledges. "But the payoff would be profound."

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