Confirming the origin of the recent 'intriguing' radio signal detected by SETI remains challenging, mainly because it appeared only once. Multiple telescopes working in tandem would enable far more precise tracking in future observations.
Just days ago, astronomers using Australia's Parkes radio telescope announced an 'intriguing' narrowband signal potentially originating from Proxima Centauri, our nearest star system. This discovery sparked widespread interest in the scientific community for compelling reasons.
Proxima Centauri hosts Proxima b, an Earth-sized rocky planet in its star's habitable zone. The signal occupied a remarkably narrow frequency range of 982 MHz—a bandwidth no known natural phenomenon can produce. To date, the only confirmed sources of such narrowband emissions are technological, like human satellites.
Notably, the signal drifted slightly over hours of observation, indicating a source in motion, consistent with a planetary orbit. It also passed rigorous automated filters designed to eliminate terrestrial interference.
These traits align precisely with what SETI researchers have sought for decades. Yet, the team cautions that much verification remains. 'It has special properties that passed many of our tests, and we can't explain it yet,' Andrew Siemion of UC Berkeley told Scientific American.
Dubbed Breakthrough Listen Candidate 1 (BLC-1) and detected in spring 2019, this signal advances the search for extraterrestrial intelligence—but highlights limitations in current methods, as noted by Michael Garrett, director of the Jodrell Bank Centre for Astrophysics, in The Conversation.
Observed only once, it evades detailed follow-up. Without repetition, skeptics can reasonably attribute it to novel human interference or instrumental artifacts, Garrett explains.
Traditional SETI relies on single-dish telescopes like Parkes, ideal for wide-sky surveys but poor for localization. Although aimed at Proxima Centauri, its field included hundreds of thousands of stars, any of which could host the signal's source.
Garrett proposes using multiple large dishes separated by thousands of kilometers. Combining their data via very long baseline interferometry (VLBI) yields pinpoint accuracy. 'For nearby systems like Proxima Centauri, we can locate signals to within one-thousandth of an astronomical unit, identifying the host planet,' he states.
This setup also rules out Earth-based interference due to the vast separations.
Challenges include processing immense data volumes—a few minutes' observation generates several terabytes (1 TB = 1,024 GB)—demanding substantial computational power. SETI's conservative approach adds hurdles.
Progress looms: Breakthrough Listen eyes MeerKAT (64 antennas in South Africa) and the Square Kilometre Array (SKA) for enhanced surveys.
