A thorough search for sentient life elsewhere in the Milky Way has turned up no evidence of extraterrestrial activity, implying that we may be the galaxy’s solitary occupants. Researchers searched millions of stars and hundreds of exoplanets but were unable to find a single technological signal from another world. The lonely search is documented in four independent studies published over the last nine years, the most recent of which was just made available as a preprint and is currently undergoing peer review. The researchers use the Murchison Widefield Array in Australia to seek technosignatures elsewhere in the Milky Way in each episode.
Technosignatures are signs of technological use, and their finding in space would almost probably mean that the Search for Extraterrestrial Intelligence has been successful (SETI). While these traces can take various forms, the researchers focused on low-frequency radio waves because they are thought to be among the first electromagnetic signals created by an alien civilisation. “Low-frequency radio waves, such as those utilized by FM radio, are a widespread choice for communications on Earth,” write the study’s authors. Aliens “would only need to be able to build a massive dish” to create such a signal, leading the researchers to conclude that “the most appetizing signal from another planet would be a powerful military satellite.”
The first three studies in the series failed to find low-frequency radio waves coming from the galactic center (GC), the Orion Molecular Cloud, or the Vela supernova remnant. Researchers returned to the GC in the most recent chapter, but this time scanned a larger section of the sky. “The Galactic Centre (GC) is a prime SETI target,” they add, “since the line of sight toward the GC contains the biggest integrated count of Galactic stars in any direction.” Furthermore, “in the inner regions of the Galaxy, the fraction of stars with a habitable planet is largest,” all of which points to the GC as the most likely home for extraterrestrial life.
The study authors conducted a blind survey of 3.3 million stars after focusing their search on 144 exoplanetary systems in the GC. Unfortunately, they came up empty-handed. They clarify, “No plausible technosignatures have been discovered.” As depressing as this discovery is, it does not show that we are alone in our galaxy. It’s possible that life exists in an as-yet-undiscovered sector of our galaxy, or that we simply haven’t evolved the technology to detect it.
Still, the radio silence observed in all four studies adds to the perplexingly incomprehensible Fermi paradox, which explains the apparent contradiction between our lack of contact with aliens and the overwhelming possibility that extraterrestrial civilizations exist. After all, the cosmos contains so many potentially livable planets, and given our galaxy’s age, it’s extremely conceivable that someone, somewhere, has perfected the capability to populate other worlds by now. The fact that Earth has never been visited by such a civilisation – at least not that we are aware of – is therefore perplexing, despite a multitude of speculative hypotheses.
For example, some scientists believe that due to the antiquity of the cosmos, many sentient civilizations are unlikely to exist at the same time, implying that humans may have simply missed the aliens like passing ships in the night. Whether our extraterrestrial cousins are avoiding us, haven’t evolved the technology to contact us, or simply don’t exist, researchers on Earth are determined to keep looking in the hopes of finding something.
