Scientists with the Breakthrough Listen project took up the mantle of the Search for Extraterrestrial Intelligence (SETI) several years ago, continuing the decades-long search for E.T. The project has just released its largest survey to date, consisting of more than 60 million stars…and no aliens.
There are numerous ways we might detect alien life, such as the presence of megastructures that obscure starlight or specific biosignatures in an exoplanet’s atmosphere. However, scanning for radio signals is the most efficient technique available with our current level of technology. Breakthrough Listen conducted its latest survey along a line of sight toward the center of the galaxy, taking advantage of the increasing star density to cover as many hypothetical aliens as possible.
The release is still only preliminary (you can see all the data on the preprint arXiv service), but it doesn’t look like there are any big alien surprises lurking within. Breakthrough Listen, which was funded by Russian-Israeli billionaire Yuri Milner and the late Stephen Hawking, used the Green Bank Radio Telescope in West Virginia and the Parkes Radio Telescope in Australia to sift through 600 hours of radio waves from the stars between 0.7 and 93 GHz. The team did spot a few signals likely associated with a type of highly active neutron stars known as magnetars, which will be of interest to astronomers who study such objects. But there’s nothing to suggest intelligent life.
The galactic center. The supermassive black hole Sagittarius A* is in the bright white spot to the right.
However, this doesn’t guarantee there is no intelligent life among these 60 million stars. There could be something alive out there, but they’re not attempting to communicate in a way we can detect. Specifically, the team was looking for beacons — repeating radio bursts designed to attract attention rather than accidental leakage of radio signals akin to Earth TV and radio broadcasts. They theorize that the galactic center is an ideal place to place such a transmitter.
It’s possible there is (or was) a transmitter out there, but the vastness of time and space makes the Breakthrough Listen mission exceedingly difficult. There could be alien civilizations among these 60 million stars whose signals have yet to reach Earth, or perhaps they’ve become so advanced they no longer use radio waves, and their radio “bubble” has long since passed us. On galactic scales, these civilizations may only be detectable for brief slivers of time and only if you know where to look. But we’re going to keep looking because knowing we are not alone in the universe could change everything.
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