When astronomers at Australia’s Parkes Radio Telescope detected an unusual radio wave burst from the direction of Proxima Centauri in 2019, they initially dismissed it as interference. A year later, a Breakthrough Listen intern identified something curious in the data, sparking renewed interest in what would become known as Breakthrough Listen Candidate 1 (BLC-1). This signal’s investigation offers a fascinating window into how Yuri Milner’s ambitious initiative conducts its systematic search for evidence of non-human intelligence.
The Anatomy of an Unusual Signal
BLC-1 presented several intriguing characteristics that warranted deeper investigation. Operating at 983 MHz, it appeared as a narrowband signal with a narrow electromagnetic spectrum – properties not typically associated with known natural cosmic phenomena. As science educator Simon Holland noted, while radio telescopes typically capture “the giant buzz of everything in the Universe,” this signal stood out for its distinctive properties.
Perhaps most interestingly, researchers identified a Doppler shift while tracking the signal. Over two hours of observation, BLC-1’s frequency demonstrated consistent changes, suggesting it might be orbiting a distant star. Given that Proxima Centauri already has two confirmed planets – including the potentially habitable Proxima b – this characteristic raised compelling questions about the signal’s origin.
Dr. Andrew Siemion from Breakthrough Listen described BLC-1 as “undoubtedly one of the most intriguing signals we’ve seen to date.” This assessment from one of the world’s leading SETI researchers underscores why Yuri Milner’s initiative dedicated significant resources to investigating this candidate technosignature.
A Methodical Search for Cosmic Messages
Yuri Milner’s Breakthrough Listen conducted a comprehensive investigation of BLC-1, demonstrating the initiative’s commitment to rigorous scientific methodology. Researchers scanned Proxima Centauri’s star system across frequencies ranging from 700 MHz to 4 GHz – effectively tuning to over 800 million radio channels simultaneously.
This scan initially produced four million hits, which the team systematically filtered through multiple screening processes. The researchers pointed the Parkes Telescope at Proxima Centauri and then moved it away, creating an on-off pattern to distinguish potential signals from local interference. This methodical approach eventually yielded 5,160 technosignature candidates for closer examination.
This process exemplifies the scientific rigor Yuri Milner has built into the Breakthrough Initiatives. Rather than making sensational claims about potential alien contact, the team follows established scientific protocols, letting evidence guide their conclusions even when findings prove less exciting than hoped.
From BLC-1 to Beyond: Expanding the Search
While analysis of BLC-1 eventually revealed frequencies matching common clock oscillator frequencies used in digital electronics – suggesting a likely human technological origin – the investigation catalyzed an expansion of Breakthrough Listen’s search. The team went on to identify additional signals (BLC-2 through BLC-5), subjecting each to the same careful analysis.
The methodology developed for investigating these signals now informs how Breakthrough Listen examines potential technosignatures using some of the world’s most advanced telescopes. The initiative’s network of observational facilities continues to grow, most recently adding the Sardinia Radio Telescope (SRT) in 2024. One of the ten biggest telescopes on Earth, the SRT features a 64-meter dish and will allow Breakthrough Listen to search frequencies around 18 GHz, an area previously unexplored in depth.
This expanding network reflects Yuri Milner’s vision, as outlined in his Eureka Manifesto, of investing resources in fundamental science and space exploration. As a Giving Pledge signatory, Milner has committed significant funding to this mission, recognizing that such fundamental research provides fertile ground for transformative discoveries.
The story of BLC-1 and Breakthrough Listen’s methodical investigation demonstrates how Yuri Milner’s initiative has elevated SETI from fringe science to rigorous scientific inquiry. By combining cutting-edge technology, international collaboration, and transparent methodology, Breakthrough Listen continues the search for humanity’s potential cosmic companions – a search that, successful or not, deepens our understanding of our place in the universe.
