Do aliens use a quirk of the sunthe gravity to transmit information through an interstellar communication network? For the first time, astronomers investigated this intriguing possibility and scanned for signals coming from hidden non-human probes around the sun.
So far, the method has not shown signs of space-traveling aliens, but it represents a promising new way of hunting aliens as part of the search for extraterrestrial intelligence (SETI).
The new search strategy is based on the findings of Albert Einstein, who showed in 1915 that gravity deforms the fabric of space-time. This means that massive objects, such as stars and galaxies, bend light around them. This effect, known as gravitational lensing, allows scientists to see extremely distant objects whose light has been distorted by enormous foreground galaxies and galaxy clusters.
“It’s a lot like a magnifying glass,” Nicholas Tusaygraduate student at Penn State, told Live Science.
With both a gravitational lens and a magnifying glass, the magnification works best when a person or detector is positioned at a specific location known as the focal point, he said.
The sun’s gravitational focus begins at about 550 astronomical units (AU), or 550 times the distance between Earth and the sun, Tusay said. A telescope placed at this location would have amazing capabilities – it could resolve continents and mountains on a planet orbiting another star, he added.
“Light goes both ways,” Tusay said. “If you can magnify light coming at you, you can also magnify light going out.”
This means that gravitational lensing can also be used to efficiently send signals across interstellar distances, so scientists speculated about technological aliens who place probes at the foci of stars, effectively turning them into a giant point-to-point communication network.
To test this idea, Tusay and his colleagues used the Green Bank Telescope in West Virginia to make six five-minute scans for radio signals coming from the sun’s gravitational focus. And what did they find?
“Nothing,” he said. “To state it precisely: In the frequencies that we observed, during the time that we observed, we found no convincing signals that were extraterrestrial in origin.”
The results were published last summer in The Astronomical Journal and were presented last week by Tusay at the 241st meeting of the American Astronomical Society in Seattle.
While the findings are not yet proof of ET, Tusay said it is possible that extraterrestrial probes placed at the sun’s gravitational focus only turn on from time to time. And other stars have properties that make them better nodes in a giant space internet, so these could be additional search targets, he added. He sees the method as more of a proof-of-concept that could present something interesting if conducted for longer and with more resources.
“We’re always talking about new ways to search in the SETI field,” Julia DeMarines, an astrobiologist at the University of California, Berkeley, who was not involved in the work, told Live Science. “This is the first time I’ve seen a search dedicated to this specific possibility of intercepting messages.”
When nothing is seen in a SETI search, it could mean several things, she added, including that no one is out there communicating, or simply that no one is communicating in this way. Any new search method is always welcome, DeMarines said. “If you don’t look,” she added, “then you’ll never know.”
