Alien hunters turn their attention to the heart of the Milky Way

A team of researchers from Cornell University and the SETI Institute has developed a new technique to hunt for repetitive signals from the middle of the Milky Way.
Christopher McFadden
Could the center of the Milky Way be harboring alien civilisations?


Scientists are turning to the center of the Milky Way to look for potential signs of intelligent alien life. Published in The Astrononmical Journal, a new study shows how scientists are hunting for narrow-frequency radio pulses emanating from within our galaxy that could reveal the existence of aliens. Pulsars naturally emit these pulses but they also happen to be used by our species for certain technologies like radar.

As these pulses are very conspicuous and tend to stand out from the background noise of space, they could, scientists argue, be a great way to communicate over long distances. If their hypothesis is correct, the theory goes, we should be able to scan for them and potentially eavesdrop on distant alien civilizations' conversations.

And so, a group of researchers with Akshay Suresh (a graduate student from Cornell University) as the lead, has created software capable of identifying just these sorts of recurring frequency patterns. The team tested the software on known pulsars to ensure that it can accurately detect the narrow frequencies, which are significantly smaller than those utilized by a standard FM radio station. Subsequently, they utilized the software to analyze data from the Green Bank Telescope in West Virginia.

"Until now, radio SETI has primarily dedicated its efforts to the search for continuous signals," study coauthor Vishal Gajjar of the SETI Institute, a nonprofit organization dedicated to the search for intelligent life in the universe, said in a statement. "Our study sheds light on the remarkable energy efficiency of a train of pulses as a means of interstellar communication across vast distances. Notably, this study marks the first-ever comprehensive endeavor to conduct in-depth searches for these signals," he said.

The team is focussing their studies on the middle of the Milky Way galaxy due to its high concentration of stars and the possibility of finding habitable exoplanets. Additionally, intelligent extraterrestrial life located in the core of the galaxy could easily communicate with other planets by sending signals across a vast range. By using narrow bandwidths and repeating patterns, these aliens could potentially expose themselves, as such a combination is highly improbable in natural occurrences according to Steve Croft, a project scientist with the Breakthrough Listen program and co-author of the study.

Using an algorithm, the new scanning technique can swiftly search through 1.5 million telescope data samples within 30 minutes. Despite not detecting any significant indications during the initial search, researchers believe that the algorithm's speed will enhance future exploration endeavors. "Breakthrough Listen captures huge volumes of data, and Akshay’s technique provides a new method to help us search that haystack for needles that could provide tantalizing evidence of advanced extraterrestrial life forms," Croft added. 

You can view the study for yourself in the journal The Astronomical Journal.

Study abstract:

Radio searches for extraterrestrial intelligence have mainly targeted the discovery of narrowband continuous-wave beacons and artificially dispersed broadband bursts. Periodic pulse trains, in comparison to the above technosignature morphologies, offer an energetically efficient means of interstellar transmission. A rotating beacon at the Galactic Center (GC), in particular, would be highly advantageous for galaxy-wide communications. Here, we present blipss, a CPU-based open-source software that uses a fast folding algorithm (FFA) to uncover channel-wide periodic signals in radio dynamic spectra. Running blipss on 4.5 hr of 4–8 GHz data gathered with the Robert C. Byrd Green Bank Telescope, we searched the central  of our galaxy for kHz-wide signals with periods between 11 and 100 s and duty cycles (δ) between 10% and 50%. Our searches, to our knowledge, constitute the first FFA exploration for periodic alien technosignatures. We report a nondetection of channel-wide periodic signals in our data. Thus, we constrain the abundance of 4–8 GHz extraterrestrial transmitters of kHz-wide periodic pulsed signals to fewer than one in about 600,000 stars at the GC above a 7σ equivalent isotropic radiated power of ≈2 × 1018 W at δ ≃ 10%. From an astrophysics standpoint, blipss, with its utilization of a per-channel FFA, can enable the discovery of signals with exotic radio frequency sweeps departing from the standard cold plasma dispersion law.

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