Progress of radio search for extraterrestrial intelligence technosignatures

Based on the Copernican principle, Drake’s formula and the discovery of a large number of exoplanets, most scientists believe that there must be life outside the Earth, especially advanced intelligent life (or civilization). Because of the advantages of radio technology, it has become one of the best means to search for extraterrestrial intelligence (SETI). China’s “eye in the sky”, Five-hundred-meter Aperture Spherical radio Telescope (FAST), is the largest single-aperture radio telescope in the world, and SETI is one of its five scientific goals. Its extremely high sensitivity in low frequency radio L-band is of great significance to SETI. Based on the backend equipment of FAST for SETI observation and observing time for FAST, we carry out SETI backend commensal survey observations and exoplanet targeted observations. We find two groups of candidates that demonstrate this RFI mitigation and candidate selection, and validate our SETI instrumentation techniques as well as our data processing pipeline. Cooperating with SETI@home and Breakthrough Listen Team at Berkeley, we develop multibeam coincidence matching (MBCM) strategy and polarization and frequency drift criteria that make the ETI signal identification process more scientific and complete, and conduct observation and data processing to screen ETI candidate targets. We also find a signal at 1140.604 MHz detected from the observation toward Kepler-438 originally piqued our interest that is roughly consistent with assumed ETI technosignatures. However, its polarization characteristics are able to eliminate the possibility of an extraterrestrial origin. Our observations achieve an unprecedented sensitivity. In addition, we also study the drift rate that is contributed by the rotations and orbits of Earth and the exoplanet in the celestial mechanics perspective, and obtain the expected pseudosinusoidal drifting result with both long-term observations and shorter orbital periods of exoplanets. The characteristics of pseudosinusoidal curves can be applied to long-term SETI reobservations in the future research as another new criterion for extraterrestrial signals. This paper mainly introduces the history of SETI observation in the world, especially the status quo and latest progress of SETI research conducted by FAST, and its future prospects.