SETI Institute applies game theory to time radio search at antisolar point; 2023 pilot found no signals

The SETI Institute has announced a new approach to searching for extraterrestrial civilizations that uses game theory to predict when a signal might be sent, according to Nauka w Polsce. The work relies on the Allen Telescope Array (ATA) at the Hat Creek Radio Observatory in Northern California, USA. The researchers have begun a multi-year search focused on one place in the sky: the antisolar point, which lies exactly 180 degrees from the Sun as seen by the observer naukawpolsce.plNauka w Polscenaukawpolsce.plOpen source ↗.

The strategy is described in a paper in The Astronomical Journal, whose first author is Sofia Sheikh of the SETI Institute. The paper also presents preliminary pilot results, which so far have provided no evidence of extraterrestrial technology.

Schelling point as a meeting place

Game theory studies optimal behavior when interests conflict or when decisions must be coordinated with others. It includes the notion of a Schelling point: a choice two parties can make independently when they must coordinate but cannot communicate beforehand.

The SETI researchers argue that the configuration of the Solar System can give both sides such a reference point. A distant civilization could observe transits of Earth across the Sun, as Earth-based astronomers do for many exoplanets. At mid-transit, Earth lies exactly between the Sun and an observer in another planetary system. From Earth, that observer would be in the direction of the antisolar point, so both sides could independently regard this as a good moment for contact naukawpolsce.plNauka w Polscenaukawpolsce.plOpen source ↗.

Observation plan and pilot results

The antisolar point moves against the background stars as Earth orbits the Sun, so observations are to be repeated throughout the year over several years. This differs from typical searches, which usually target specific stars and planetary systems. The plan calls for two or three nights per week over four years, and an automated pipeline has been built to handle the large data volume.

Before the main campaign, pilot observations were made over three nights in 2023. Using 20 ATA antennas, about 17 hours of observations produced 32 terabytes of data. Initial analysis found about 1.9 million signal detections. After filtering and checking the most promising ones, no signals matching potential technosignatures were found; all detections were explained by radio interference from human sources.

The team also determined the sensitivity of the pilot. For a transmitter like the planetary radar of the former Arecibo radio telescope, signals could be detected from distances of up to 124 light-years naukawpolsce.plNauka w Polscenaukawpolsce.plOpen source ↗.