In hunt for E.T., a giant leap

Up to now, he and his colleagues at Harvard and Princeton University have observed 15,000 stars and come up empty. But they now are building a 72-inch telescope that will allow them to survey large patches of sky at a time. They plan to begin operating the telescope - funded by a $350,000 grant from the Planetary Society in Pasadena, Calif. - within a year. Other teams at facilities such as the Lick Observatory in California are also running more selective searches.

One wavelength of emerging interest lies in infrared light, which falls just below visible light on the electromagnetic spectrum. Looking in that wavelength regime was first proposed by Freeman Dyson of the Institute for Advanced Study in Princeton, N.J. In 1959, he suggested that advanced civilizations might build orbiting habitats and solar-power stations that formed a "shell" around a star at a distance that matched that of the civilization's home planet. Such a "Dyson Sphere" would emit large amounts of infrared radiation, giving the star the appearance of emitting too much infrared light.

At the time, it sounded like an intriguing approach. But astronomers have since learned that sunlike stars - especially those with disks of dust and gas surrounding them - can appear to generate too much infrared radiation for their type.

Dr. Werthimer and colleague Charles Conroy have taken an initial crack at looking for excess IR by picking sunlike stars that are too old to have protoplanetary disks. Instead of bidding for precious telescope time, they mined data archived from surveys taken by ground- and space-based infrared telescopes.

While they found 32 stars that might have been Dyson Sphere candidates based on infrared readings alone, they found no unusual radio emissions or light pulses from 20 of the stars observed at the Arecibo Radio Telescope in Puerto Rico or from 25 of the stars viewed at optical observatories.

Other scientists are contemplating the possibility of searching for pulses from infrared lasers. Such lasers might be a preferred means of sending signals or setting up beacons across the galaxy because the light penetrates interstellar dust that can block visible light, researchers say.

Trying to expand efforts to cover a range of wavelengths and transmission types as the technology becomes available may seem like casting good money after bad. But limiting searches to one form of communication or to one type of search strategy is futile, Werthimer counters. "It's naive to think we know exactly what E.T. is doing."

• From 1947 to 1969, the US Air Force studied UFOs under Project Blue Book, headquartered at Wright-Patterson Air Force Base in Ohio. Of 12,618 total sightings reported to Project Blue Book, 701 remain unidentified.

• During several space missions, NASA astronauts reported phenomena they could not explain; NASA later determined that, in the context of space, none of the observations could be termed abnormal.

• Congress ended funding for NASA's High Resolution Microwave Survey in 1993; as a result, SETI launched the private nine-year Project Phoenix, which ended in March.

• Project Phoenix searched more than 750 nearby stars for radio signals.

Sources: NASA, SETI

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