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17 Jun 2002
US astronomers are relying on lasers to make first contact with aliens.
The search for extraterrestrial intelligence has just moved into a new dimension. US-based scientists from the University of California's Lick Observatory, the Universities of Santa Cruz and Berkeley and the Search for Extraterrestrial Intelligence (SETI) Institute, California are looking for laser pulses as well as radio transmissions in their quest to find new life.
"This is perhaps the most sensitive optical SETI search yet undertaken," said Frank Drake, chairman and co-investigator at SETI, "We are looking for brief but powerful pulses of laser light from other planetary systems, rather than the steady whine of a radio transmitter."
Drake and the team coupled the Lick Observatory's 40 inch Nickel Telescope with a new pulse-detection system that is based on three photomultipliers. Light entering the detector is split into three beams and then transferred to each of the photomultiplier tubes. Counters in a "discriminator box" monitor single and coincident pulses from each of these channels. Assuming that an extraterrestrial civilization is deliberately signalling our solar system, the team can detect bright light pulses only a billionth of a second long from a source many light years away.
Previous optical SETI experiments based on only two photomultipliers have been plagued by false alarms from the stray photons of cosmic rays or starlight. However, Drake and the team are certain that their new approach will produce a "clean" experiment with less ambiguous results.
Although listening for radio signals continues, the team believes that the huge information capacities of lasers could make them a preferred interstellar communications system for any advanced extraterrestrial intelligence that is trying to make contact.
"[Another] advantage of optical SETI is that there's no terrestrial interference," added Drake. "This is an exciting new field."
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