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The search for extraterrestrial life in this vast universe needs all hands on deck. A crowd-sourced project from UC Berkeley called on volunteers to lend their home computers to search for signs of aliens, and now scientists have narrowed it down to 100 signals of interest.
The SETI@home project—short for the Search for Extraterrestrial Intelligence—ran from 1999 to 2020 and relied on volunteers’ home computers to process radio signals from space. More than 12 billion potential signals were collected during the course of this project. The SETI@home team spent 10 years analyzing these signals, narrowing them down to around a million of interest before coming up with a final list of 100 radio signals that now require a deeper look.
Nothing may come of all this, but that doesn’t mean SETI hasn’t taken a big step forward as a result of this ambitious project.
“If we don’t find ET, what we can say is that we established a new sensitivity level. If there were a signal above a certain power, we would have found it,” David Anderson, computer scientist and co-founder of SETI@home, said in a statement. The results from the project are published in two papers in The Astronomical Journal.
Phone home
The project asked volunteers to install software on their home computers, allowing the team to analyze data gathered by the now-defunct Arecibo Observatory in Puerto Rico in search of unusual radio signals.
Over a period of 21 years, millions of people from around the world signed up to help search for alien signals. “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,” Anderson said. “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 idea was to break down a massive amount of data—normally the kind processed by supercomputers—into smaller chunks that could be handled by many home computers. The data was recorded passively as astronomers pointed Arecibo’s radio dish at different areas of the sky and then distributed to the various home computers.
The SETI@home software would then manipulate the data using a mathematical tool known as the discrete Fourier transform, which shows which frequencies make up the radio signals. The software then scanned the data for changes in frequency based on the relative motion of the source, a phenomenon known as Doppler drift.
Signal interference
The project initially turned up 12 million signals, but the scientists behind the project had to figure out a way to narrow them down. “Until about 2016, we didn’t really know what we were going to do with these detections that we’d accumulated,” Anderson said. “We hadn’t figured out how to do the whole second part of the analysis.”
The team used a supercomputer provided by the Max Planck Institute for Gravitational Physics in Hanover, Germany, to eliminate radio frequency interference and noise. That narrowed the number of signals down to a couple of million, and those were vetted once again to eliminate ones coming more or less from the same place in the sky or at the same frequency.
The final thousand signals had to be assessed manually, and the team came up with the final 100 candidates deemed worthy of further investigation. “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,” Eric Korpela, astronomer and SETI@home project director, said in a statement. “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 final analysis of the project is still to come.
