The close encounter will have to wait. Astronomers have come up empty-handed after scanning the heavens for signs of intelligent life in the most extensive search ever performed.
Researchers used ground-based telescopes to eavesdrop on 1,327 stars within 160 light years of Earth. During three years of observations they found no evidence of signals that could plausibly come from an alien civilisation.
The only signals picked up by the Green Bank telescope in West Virginia and the Parkes telescope in Australia had more Earthly origins, the scientists found, with mobile phones and other terrestrial technology providing plenty of noise, and more transient signals coming from overflying satellites.
“It’s quiet out there,” said Danny Price, an astronomer at the University of California, Berkeley, and a member of the Breakthrough Listen project, which aims to scan a million nearby stars, the entire plane of the Milky Way, and 100 neighbouring galaxies for radio and optical signals.
“We haven’t found anything in the data, but I’m certainly not giving up hope. There are still so many more stars to look at and more search approaches to consider.”
The scientists hope to spot “technosignatures”, which could reveal the presence an alien civilisation. These powerful electromagnetic signals are distinct from the various bursts of natural radiation that pour constantly through the galaxy.
Unlike the broad bursts that come from stars and other cosmic objects, powerful and narrow technosignatures might be produced by alien communications or propulsion systems, the scientists say.
During the three-year effort, the astronomers scanned billions of radio channels and filtered out any signals that appeared to come from nature or equipment on Earth. Having dismissed millions of signals this way, the team was left with only a handful of “events”. On closer inspection, these too turned out to have prosaic explanations.
The Breakthrough Listen team described their latest attempt to track down ET in two papers released on Tuesday, which made all the data available to the public. “There could be a signal in the data that we didn’t detect this time around, but others can now look through it to see if we missed anything,” Price said.
Teegarden’s star (in red) and its two planets are located 12.5 light years from our solar system. Photograph: Courtesy of Institute for Astrophysics/University of Göttingen