SETI May Be Searching Wrong Frequencies: New Study Explained

Astronomers searching for extraterrestrial intelligence may have been tuning their receivers to the wrong part of the radio spectrum for over six decades. New research from the University of Manchester suggests that the narrow frequency band traditionally used by SETI projects worldwide — the so-called 'water hole' between 1.42 and 1.66 GHz — could be causing scientists to overlook promising signals at higher frequencies. 'The expectation is that the universe should be teeming with life, and we should be able to find radio signals from it,' says Rob van den Berg, space expert at the Sonnenborgh Observatory in Utrecht. 'But so far, we have searched in a very limited way.'

Why astronomers have searched the 'water hole' for decades

Since the birth of modern radio astronomy and SETI in the 1960s, most searches for alien technosignatures have concentrated on a narrow frequency window between 1.42 GHz (emission line of neutral hydrogen) and 1.66 GHz (emission line of hydroxyl). Scientists reasoned that any civilization capable of interstellar communication would naturally choose this 'quiet' region of the spectrum, located between the two chemical constituents of water — hence the name 'water hole'. The logic was compelling: water is essential for life as we know it, and hydrogen is the most abundant element in the universe.

However, this approach has effectively ignored vast swaths of the radio spectrum. 'For decades, SETI surveys have focused on a relatively small slice of the radio spectrum. We wanted to know what would happen if we looked somewhere completely different,' explains Louisa Mason, a PhD researcher at the Jodrell Bank Centre for Astrophysics, University of Manchester.

First-ever SETI survey using the ALMA telescope

Mason conducted the first SETI search ever carried out using the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile — the world's most powerful radio telescope operating at millimeter and submillimeter wavelengths (35–950 GHz). Unlike traditional SETI instruments that listen in the gigahertz range, ALMA probes frequencies 10 to 100 times higher. Mason's team mined archived ALMA observations, originally recorded for other astronomy projects, and analyzed them for narrowband signals that could indicate artificial technology.

The results, presented on 24 July 2026 at the Royal Astronomical Society's National Astronomy Meeting in Birmingham, revealed no candidate technosignatures. But the null result is not a disappointment — it opens a new frontier. 'This research opens up a completely new part of the search space,' Mason said. 'It shows we can search effectively at these higher frequencies, and that archived telescope data hold enormous untapped potential.'

6.1 million stars: the 'stellar bycatch' surprise

One of the most striking findings emerged when Mason reanalyzed data from a previous Breakthrough Listen survey that had targeted 1,327 pointings. Using the Gaia star catalogue, astronomers had estimated they examined about 288,000 stars. But when Mason applied the Besançon Galactic Model — a sophisticated simulation of the Milky Way — the number skyrocketed to over 6.1 million stars, a factor of 21 higher. 'One of the most exciting outcomes is that we have examined many more stars than we initially thought,' Mason noted.

This 'stellar bycatch' effect occurs because radio telescopes capture signals from all stars within their field of view, not just the intended target. The finding suggests that previous SETI campaigns, including those by Breakthrough Listen and other major initiatives, may have been far more comprehensive than their original statistics suggested — though still confined to the same narrow frequency band.

What this means for the future of alien hunting

Mason and her colleagues emphasize that the absence of a detection does not mean intelligent extraterrestrial life does not exist. The study encompassed only a small number of observations and two limited frequency ranges. The key takeaway is that SETI should expand its search across a broader portion of the radio spectrum, leveraging archived data from telescopes originally designed for other astrophysical purposes.

Computational power has also been a bottleneck. 'The data volumes are enormous. But now we can use artificial intelligence to search for signals,' says Van den Berg. Machine-learning algorithms can sift through petabytes of archival telescope data far faster than human researchers, potentially identifying patterns that traditional analyses would miss.

Frequently Asked Questions

What is the 'water hole' in SETI?

The 'water hole' is the radio frequency range between 1.42 GHz (hydrogen emission line) and 1.66 GHz (hydroxyl emission line). Since hydrogen and hydroxyl combine to form water, this region has been considered a natural meeting point for interstellar communication, and has been the primary focus of SETI searches since the 1960s.

Why did astronomers use ALMA for SETI?

ALMA operates at much higher frequencies (35–950 GHz) than traditional SETI instruments. By searching these millimeter and submillimeter wavelengths for the first time, researchers can explore an entirely new part of the radio spectrum that has been overlooked for decades.

What is 'stellar bycatch'?

Stellar bycatch refers to stars that are unintentionally captured in a telescope's field of view during an observation aimed at a different target. Reanalyzing archived data with more sophisticated galactic models revealed that a single 1,327-pointing survey actually covered over 6.1 million stars, not the 288,000 previously counted.

Does this mean there is no alien life?

No. The study explicitly states that not finding a signal does not rule out the existence of extraterrestrial intelligence. The search only used a small number of archived observations and two narrow frequency bands. It simply shows that astronomers need to broaden their search strategy.