The hunt for aliens is not as sensational or speculative as you might think. In fact, astronomers are constantly coming up with practical ways to look for intelligent life in our universe. Research recently published in the Astronomical magazine describes a groundbreaking method to search for radio beacons in the center of the Milky Way – a new idea about how aliens can send us signals. (Spoiler: The study authors haven’t found any beacons yet!)
Astronomers have been scanning the sky with radio telescopes since tThe search for extraterrestrial intelligence beginsor SETI, in the 1960s, when they started listening to technological messages from the stars. In particular, they have been looking for so-called narrowband signals – flashes of radio waves that occur over a very narrow frequency range, which nature cannot produce. Narrowband messages generally need to target a specific star, while a centralized radio beacon can cast a wide net that sweeps across the galaxy.
“This paper is hugely important to the search for extraterrestrial intelligence because it contains the first major study of radio technology signatures that are periodic,” said SETI Institute astronomer. Sofia Sheikh, a co-author of the new work. Periodic means these signals would “blink over time like a lighthouse,” she says, “rather than assuming the signal should be on continuously like a streetlight.”
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Sheikh and other collaborators, including the Cornell University astronomer Akshay Suresh, suggest that these repetitive pulses of radio emissions could be coming from some kind of flashing light. If located at the center of the galaxy, such a beacon could be a particularly efficient way to communicate over great distances. The signals from these types of beacons may also be easier to find while sifting through radio data, which are often tainted by the ubiquitous hum of Earth’s technology.
These beacons would be more energy efficient compared to the continuous narrowband signals that astronomers have previously been looking for. What’s more, “their regularly blinking nature makes them easy to detect with algorithms, distinguishable from human-induced radio interference, and generally obvious as something strange,” Sheikh explains. Looking at the galactic center is also a great way to increase your chances of seeing something, as the concentration of stars is higher in the center of the Milky Way. More stars means more planets and more opportunities for life to emerge.
“It’s a logical technique to look for events or broadcasts that we can’t otherwise predict,” the Penn State astronomer agrees. Macy Houston, which is not affiliated with the findings. But there’s a catch: Although the center of the galaxy is densely populated with stars, many astronomers predict that the radiation there makes it too dangerous for life to emerge, putting it outside the so-called Galactic habitable zone.
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That didn’t stop Sheikh, Suresh and their teammates, who used the world’s largest steerable radio dish, the Green Bank Telescope in West Virginia to test their probe for galactic beacons. After five hours of looking at the central 600,000 stars in the Milky Way, nothing particularly jumped out at the data. However, this amount of searching is like exploring a single drop of water plucked from an entire swimming pool; just because nothing turned up in this initial search doesn’t mean the theory of galactic beacons has failed. Suresh is especially pleased that the algorithm developed for this search will enable astronomers to easily “examine their data for pulsating signals” in future scans.
“The jury is still out on the overall prevalence of technological life in the universe,” says Sheikh. While progress may be slow, steadily trawling the entire pool of stars in the Milky Way is the only way “that we will ever be able to say anything definitive about the prevalence of technological life, and this paper takes us a step closer. ”