November 3, 2026, Mountain View, CA -- Finding a signal from an extraterrestrial civilization takes more than just pointing a telescope in the right direction. We may also need to listen at exactly the right time.
Scientists at the SETI Institute are trying a new approach to this challenge. They are combining astronomy and game theory to predict when another civilization might decide to send a message to Earth.
Using the SETI Institute's Allen Telescope Array (ATA) at the Hat Creek Radio Observatory in Northern California, researchers have launched a multiyear search focused on a particular location in the sky known as the anti-solar point. Their approach is based on the idea that two civilizations, even without communicating beforehand, might independently identify the same time and place to establish contact.
A new paper, A Large-Scale Technosignature Survey of the Anti-Solar Point with the Allen Telescope Array: Survey Design and Pilot Results, describes the campaign's strategy and presents findings from its first observations.
The pilot study did not find evidence of extraterrestrial technology, but it marked an important milestone: the first observational search of the anti-solar point, putting a decades-old scientific proposal to the test for the first time and establishing a foundation for a much larger survey.
What If Both Civilizations Had the Same Idea?
In game theory, a Schelling point is a choice that two parties might independently make when they need to coordinate without communicating.
Imagine you agree to meet someone in New York City but don't set a time or place. Both of you might choose to meet at noon at Grand Central Terminal, since it's a well-known spot and a common meeting place.
The same principle could apply to communication across interstellar distances.
An extraterrestrial civilization that wants to contact Earth might save energy by sending a focused radio signal at a specific time instead of broadcasting all the time in every direction. But how would it pick a time when someone on Earth might be listening?
The research team suggests that the layout of the solar system could give both sides a common reference point.
From certain locations in the galaxy, an observer could detect Earth passing in front of the Sun, an event astronomers call a transit. This would reveal not only Earth's existence but also information about its orbit and its position in the Sun's habitable zone.
At the midpoint of that transit, Earth would lie directly between the distant observer and the Sun. From Earth's perspective, the transmitter would appear in the direction opposite the Sun: the anti-solar point.
Because both civilizations could independently recognize this alignment, it offers a possible way to coordinate communication without having exchanged a message.
This idea does not assume that extraterrestrial civilizations exist or that they would use this strategy. Instead, it gives scientists a clear and testable idea about where and when to search.
"The challenge in SETI isn't simply deciding where to point a telescope," said Dr. Sofia Sheikh , SETI Institute Research Scientist and co-lead author of the paper. "It's figuring out where and when another civilization might choose to transmit. The anti-solar point gives us a way to think about that problem from the perspective of a potential sender, rather than just the receiver."
Turning an Idea into a Search
The ATA is especially good for testing this idea because it was built specifically for radio SETI research. Its many antennas can work together to look for very narrow radio signals that could show signs of technology.
As Earth moves around the Sun, the anti-solar point shifts against the background stars. To keep up with it, the research team makes repeated observations all year, building up coverage over several years.
This strategy is different from usual SETI searches, which focus on certain stars or planetary systems. Instead of picking specific targets, the researchers follow a moving alignment in the sky that a possible transmitter might notice too.
The survey is planned to run two to three nights each week, aiming to cover all the important positions along Earth's orbit over about four years.
The researchers have also created an automated process to handle the huge amount of data from their observations.
"Recent development of the Allen Telescope Survey Agnostic Technosignature (ATSAT) system, SETI's efficient narrowband drifting signal search pipeline, has made finding and analyzing potential technosignatures very effective in such large radio datasets like the ASP survey," said Isabel Gerrard, Technosignature Researcher with Breakthrough Listen at the University of Oxford and co-author.
One of the biggest challenges is telling interesting signals apart from radio interference caused by human technology, such as satellites and communication systems.
The team's software looks for narrowband radio signals, checks how their frequencies change over time, and compares data from two slightly different directions. This helps them tell apart signals that seem to come from a specific spot in the sky from interference coming from nearby sources.
"Using the ATA's beamforming capability to compare signals from the ASP to a different point in the sky helps us filter out hundreds of millions of signals from human interference," said Ananya Kalapatapu, a student at Cupertino High School and SETI Institute volunteer. "Then, our researchers only have to review a compact, manageable set of the most interesting signals, helping us focus on signals with properties that are more likely to be consistent with extraterrestrial intelligence."
Researchers can then examine promising candidates and conduct follow-up observations.
What the First Observations Revealed
Before beginning the larger campaign, the team conducted a three-night pilot survey in the summer of 2023.
Using 20 antennas of the ATA, researchers collected approximately 17 hours of observations, generating 32 terabytes of data.
The first analysis found about 1.9 million radio signal detections, or "hits." After filtering and checking the most promising ones, the team did not find any signals that matched extraterrestrial technology. All the detections could be explained by radio interference from human sources.
Even though the pilot did not find a technosignature, it gave the team important information for the larger survey.
The researchers used what they learned to adjust their observing frequencies, improve how they filter out interference, and make their methods for finding signals from a specific direction even better.
The pilot also established the first observational limits for radio transmitters using the anti-solar point as a possible communication strategy. Under certain assumptions, the observations were sensitive enough to detect signals from a transmitter comparable in power to the former Arecibo planetary radar at distances of up to approximately 124 light-years.
Searching at the Right Place — and the Right Time
Searching for extraterrestrial intelligence is a huge challenge. Scientists do not know if other technological civilizations exist, what technology they might use, or if they would want to communicate.
That's why every search strategy starts with assumptions that scientists can test through observations.
The anti-solar point survey explores a simple possibility: that civilizations separated by enormous distances might nevertheless recognize the same moment as an opportunity to communicate.
This approach also shows how SETI research can use ideas from other fields, like game theory and advanced computing, to explore new possibilities.
The campaign has already gathered more than 121 nights of observations since the pilot study. Results from the first year of data will be shared in a future publication.
Even if the survey does not find signs of extraterrestrial technology, it will help scientists set new limits on possible transmissions and show which parts of the search space they have already checked.
Finding another civilization may depend not just on knowing where to look, but also on knowing when to listen. By exploring both questions, the SETI Institute is testing a new approach to humanity's search for intelligence beyond Earth.
About the Research
The paper, A Large-Scale Technosignature Survey of the Anti-Solar Point with the Allen Telescope Array: Survey Design and Pilot Results, is authored by Sofia Z. Sheikh, Eleanor Hort, and collaborators from the SETI Institute and partner institutions.
Publication: The Astronomical Journal, DOI: 10.3847/1538-3881/aeaa59
Funding: The ATA refurbishment and operations have received support from Franklin Antonio and other private and institutional contributors. The research also acknowledges support from the National Science Foundation, including support for the SETI Institute's Research Experiences for Undergraduates program.
About the SETI Institute
Founded in 1984, the SETI Institute is a nonprofit, multidisciplinary research and education organization whose mission is to lead humanity's quest to understand the origins and prevalence of life and intelligence in the universe and to share that knowledge with the world. Its research encompasses the physical and biological sciences and leverages expertise in data analytics, machine learning and advanced signal detection technologies. The SETI Institute is a distinguished research partner for industry, academia and government agencies, including NASA and the National Science Foundation.
Contact Information
Rebecca McDonald
Director of Communications
SETI Institute
