For more than sixty years, the Search for Extraterrestrial Intelligence has focused on a relatively narrow range of radio frequencies — roughly 1 to 10 gigahertz — because this is the 'quiet' part of the spectrum where natural cosmic radio emissions are weakest. The assumption has been that any intelligent civilization trying to make contact would choose these frequencies for their signals.
But a team from the University of Manchester has now conducted the first SETI survey at much higher frequencies — between 85 and 115 gigahertz — using archived data from the Atacama Large Millimeter/submillimeter Array in Chile. The results, published in July 2026, suggest that the search for alien signals may have been missing a large and largely unexplored part of the radio spectrum.
The team analyzed ALMA observations of 6.1 million stars, searching for narrow-band signals that could indicate artificial, technology-produced transmissions. While no definitive alien signals were found, the survey demonstrated that high-frequency SETI is both possible and practical. The data also revealed a surprising number of false positives from human-made interference, which will help future searches refine their filtering techniques.
The study opens a new frontier in SETI research. ALMA's sensitivity at millimeter wavelengths is extraordinary, and the telescope's archived data represents a vast, untapped resource for signal searches. The team estimates that the total SETI-relevant data in ALMA's archives could be 21 times larger than what has been searched across all other telescopes combined.
Knowledge takeaway: the first SETI survey at 85-115 GHz using ALMA data shows that high-frequency radio searches are feasible and that the archives contain 21 times more SETI-relevant data than all other telescopes combined; no alien signals were found yet, but the methodology is now proven.