Alien-hunters spot 100 ‘signals of interest’ in 21-year search for ETs

ALIEN-HUNTERS have narrowed down their 21-year-search for extraterrestrial life to 100 “signals of interest”.

The mammoth quest has seen scientists trawl through as many as 12 billion signals picked up from the darkness of space.

They’re “momentary blips of energy at a particular frequency coming from a particular point in the sky,” according to David Anderson, of UC Berkeley.

He co-founded the SETI@home project, which made it possible for the general public to help in the SETI – or Search for Extraterrestrial Intelligence.

After significant analysis that took 10 years, the SETI@home has whittled down the 12 billion signals to 100 “that are worth a second look”.

And scientists say that no matter whether they prove to be from alien life or not, it’s still valuable.

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“If we don’t find ET, what we can say is that we established a new sensitivity level,” Anderson explained.

“If there were a signal above a certain power, we would have found it.

“Some of our conclusions are that the project didn’t completely work the way we thought it was going to.

“And we have a long list of things that we would have done differently and that future sky survey projects should do differently.”

The data came from the Arecibo Observatory in Puerto Rico, which is now defunct.

Members of the public were able to download the SETI@home software to trawl this data to find unusual radio signals.

Millions of people joined in with the project between 1999 and 2020, all hunting for signs that life might be out there in the Milky Way, our home galaxy.

And they produced 12 billion detections, which UC Berkeley scientists spent a decade analysing.

Now they’re using China‘s Five-hundred-meter Aperture Spherical Telescope (FAST) to take another look at these targets to see if they can spy the signal again.

The problem for astronomers is that scanning the sky for signals produces so much information, some of which will be from radio interference.

That might come from satellites, or even sources as simple as radio and TV broadcasts or microwave ovens.

“There’s no way that you can do a full investigation of every possible signal that you detect, because doing that still requires a person and eyeballs,” said Eric Korpela, who directs the project.

“We have to do a better job of measuring what we’re excluding.

“Are we throwing out the baby with the bath water?

“I don’t think we know for most SETI searches, and that is really a lesson for SETI searches everywhere.”

The astronomers say that most searchers assume that an alien civilisation would put a lot of power into a narrow frequency band.

This would allow them to get the attention of other civilisations – like humans here on Earth.

This should be around a frequency at which astronomers observe the universe, which UC Berkeley experts say is a radio wavelength of 21 centimetres.

“This powerful narrow-band beacon would be something that’s easy to detect,” Korpela explained.

“Then, once someone had detected that, they would dedicate more observing to try and find signals near it in frequency that might be lower power and wider band that contain information.

“If we saw an extraterrestrial narrowband signal somewhere, we would probably have every telescope, radio telescope and optical telescope available pointing at that point on the sky, searching in all frequencies for anything else.

“So far we haven’t had that. If we had, I think we would all know about it.”

Although scientists haven’t found alien life just yet, the project is still seen as a major success for getting the public involved in the hunt for alien life.

“I’d say it went way, way, way beyond our initial expectations,” Anderson said.

“When we were designing SETI@home, we tried to decide whether it was worth doing, whether we’d get enough computing power to actually do new science.

“Our calculations were based on getting 50,000 volunteers. Pretty quickly, we had a million volunteers.

“It was kind of cool, and I would like to let that community and the world know that we actually did some science.”

The telescope was able to observe a third of the entire sky 12 or more times.

That covered most of the stars in the Milky Way, totalling billions.

So it was a massive help to have a million home computers lending their aid to the analysis.

Researchers were able to rank the signals by likelihood of being real, and then manually reviewed the top 1,000.

And this was then reduced to just 100.

Now researchers are scanning these signal targets using China’s FAST system, which could help to reveal if any of them have extraterrestrial origins.

But even if they don’t come up with anything, it doesn’t mean that none of the signals picked up by Arecibo were alien missives. It may have just been missed in the data.

“There’s still the potential that ET is in that data and we missed it just by a hair,” Korpela said.