4th search for aliens near Milky Way's center comes up empty

 A sweeping search for extraterrestrial technology in the middle of the Milky Way has turned up dry. 

The search, the fourth in a series looking for low-frequency radio waves that might be produced by alien civilizations, found no evidence of ET. But improvements in telescope technology mean that the strategy could be a way to find other technologically advanced societies in the future, the study authors wrote in a paper published to the preprint database arXiv on Feb. 7. 

Led by Chenoa Tremblay, a postdoctoral researcher at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia's national science agency, the researchers used the Murchison Widefield Array in Western Australia to hunt for low-frequency radio waves. Radio waves are a promising "technosignature" of extraterrestrial civilizations, the researchers wrote, because they're likely one of the first methods of long-range communications that an intelligent life-form will stumble upon. (Humans started using radio waves to communicate in the late 1800s.) 

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This was the team's fourth sweep of a large area of sky. They chose to focus on the galactic center, as this region of the Milky Way has a high density of stars. More stars mean more potential star systems, and thus more planets where life could evolve. Of course, there is a chance that this area of the Milky Way is less promising for alien life than farther reaches, the authors wrote; more stars also mean more supernovas and high-energy flares from magnetars, magnetized neutron stars surrounded by intense magnetic fields. 

Nevertheless, the team turned the telescope array toward 144 known exoplanetary systems near the Milky Way's middle. They also did a broader "blind" search of an area containing at least 3 million stars within 6,000 cubic parsecs. (A parsec is a measure of astronomical distance equal to 3.26 light-years.) This blind search also would have caught radio signals coming from more distant stars, perhaps covering billions of potential star systems. 

The researchers honed their detection for radio waves of around 155 megahertz and searched for seven hours over two nights in September 2020. 

Unfortunately for dreams of a "Star Trek"-esque federation of planets, the researchers found no sign of alien tech. But they don't intend to stop looking. The Murchison Widefield Array has since been updated to have better sensitivity, the researchers wrote, and improvements in computation may allow for searches of even larger areas of the sky. 

"Continual improvement of telescope capabilities, when combined with methodical observational campaigns, provides a means to explore the vast parameter space within which signs of technologically-capable life may be waiting to be found," they wrote in the study.

Originally published on Live Science.