Search for ETs Focuses on 166 "Promising" Signals

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Roelof Engelbrecht, a SETI@home volunteer in College Station, Texas who freely distributes an add-on feature to the screensaver program called SETI Spy that enables computers to data crunch more efficiently, said he is pleased that the researchers secured dedicated time on the Arecibo telescope.

"So far all observations have been made while piggybacking on someone else's telescope positions, but now it is SETI@home's turn, even if just for a [day]," he said.

In addition to the 166 candidates identified by SETI@home, the researchers also observed 5 extrasolar planetary systems, 35 nearby sun-like stars, 15 nearby galaxies, and 6 candidates from a second SETI Program at UC Berkeley called Serendip (Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations.)

As well as conducting a thorough analysis of the data collected over the past two weeks, the SETI@home volunteers will continue to sort through the data collected by the special receiver on the telescope and send the most interesting candidates to Berkeley for further analysis. The hope is that one day they really will find an interesting signal.

Against the Odds

Werthimer, who headed for Puerto Rico with two other colleagues while Anderson stayed in California to run the computers, is not optimistic that any of the signals are from an extraterrestrial life-form and cautions against people getting too excited. He puts the chance of success at less than 1 percent.

Since becoming involved with SETI 24 years ago, 11 of them using Arecibo's 1,000-foot (305-meter)-diameter telescope, Werthimer has re-examined several promising signals only to find out they were from a passing satellite, random noise, or some other glitch.

"I don't expect to find ET next week," he said in an interview prior to the trip. "But I am optimistic that Earthlings will find ET in the next 100 years." Technological advances, he added, are making SETI searches much more powerful.

Out of the 150 signals that were selected as the most promising candidates, Anderson said that all of them exhibit characteristics that are consistent with random noise. Given that, he too is not optimistic that ET will be encountered.

"It is really hard to put a number to it, but most people feel the odds are quite low," he said.

Nevertheless, the scientists carefully narrowed down the most likely candidates, ranking them based on criteria such as strength, whether or not the signal was detected more than once, and whether or not it is coming from a star known to have planets.

Looking for a Match

As the team re-examined the spots in the sky where the candidate signals came from, they conducted a limited amount of analysis of the data. If something very strong or interesting appeared they would have stopped the search and repeated it to make sure it was not radio pollution or some other kind of noise.

On this most current mission, nothing interesting appeared.

If the scientists do eventually find something that looks exciting, they will ask for independent confirmation of the signal by another group of astronomers using a different telescope and processing software.

"If they see something too, we can measure distance to it, train on it, then make an announcement that we found an interesting signal," said Werthimer.

Richard Factor, president of an organization dedicated to the search for evidence of extraterrestrial life called the SETI League, in Little Ferry, New Jersey is pleased that SETI@home has the opportunity to look at these 150 areas, but agreed that the chances of finding ET on this outing were slim.

"Since they stated that these candidates are about what one would expect from a statistical analysis of receiver noise, I am not unduly optimistic," he said.

Factor is optimistic that chances of finding ET in the future are good, but he is not at all impressed by the 4,287,000-plus people who have downloaded the SETI@home screensaver.

"That's less than one tenth of one per cent of the Earth's population," he said. "I should like to think that SETI is far more important than this indicates."

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