Alien hunters see the light

Looking for signs of life [Seti Institute]

Astronomers involved in the search for extraterrestrial intelligence (Seti) are broadening their hunt and looking for light signals directed at Earth.

We are looking for very brief but powerful pulses of laser light from other planetary systems

Frank Drake
Seti Institute

The optical Seti method has been tried before but previous experiments have been plagued by false alarms.

"This is perhaps the most sensitive optical Seti search yet undertaken," said Frank Drake, chairman of the board of the privately funded, non-profit Seti Institute in the US.

Mr Drake, who in 1960 conducted the first modern hunt for evidence of extraterrestrial intelligence, is usually associated with radio Seti, an approach in which large antennas are connected to specialised, multi-million channel receivers.

"This is different," he said. "We are looking for very brief but powerful pulses of laser light from other planetary systems, rather than the steady whine of a radio transmitter."

Technological boost

The Californian team says that technological improvements have made optical Seti viable, though other Seti researchers say that human limitations have hindered progress in the past.

The subject was controversial for many years with both US and Soviet observers proposing projects and wrangling over their feasibility.

Light detection has the disadvantage of only being able to detect a signal deliberately targeted at Earth, but it is less susceptible than radio Seti to terrestrial interference.

The new system uses a trio of light detectors and was designed and built by researchers at the University of California, Berkeley, and the University of California, Santa Cruz (UCSC).

Other systems have used fewer detectors and have consequently suffered from frequent false alarms.

Improved accuracy

The scientists hope that the new system, housed at the Lick Observatory at UCSC, will only suffer one false alarm a year.

They have already examined about 300 individual star systems, as well as a few star clusters.

They intend carrying on looking at least once a week for another year, they say.

Another optical Seti project, a collaboration between Princeton and Harvard Universities in the US, is also working on installing a light detector, while the optical Seti project at Columbus, Ohio, already operates a prototype system based on a 25.4-cm (10-inch) telescope.