New restrictions on hunting extragalactic technosignatures

Sep. 22 () –

A data reanalysis has imposed new restrictions on the existence of extragalactic technology firms in the search for non-terrestrial intelligence (SETI) initiatives.

Recognizing that radio surveys of nearby stars are also sensitive to cosmic background objects, in particular galaxies, groups of galaxies and clusters of galaxies, Professor Michael Garrett of the University of Manchester, in collaboration with the Director of Berkeley SETI, Dr. Andrew Siemion, have been able to establish new limits in the prevalence of very powerful transmitters in galaxies and other cosmic objects located outside our own Milky Way.

They focused on earlier observations made by the Green Bank Telescope (GBT) looking at 469 Breakthrough Listen target fields. –the initiative to find signs of intelligent life in the universe– that were located far from the gas and dust that obscure the plane of our own Milky Way. In these fields, they identify more than 140,000 extragalactic systems, including various exotic astrophysicists: interacting galaxies, various types of active galactic nuclei, radio galaxies, and various gravitational lensing systems.

Most of these sources are located at cosmological distances, but the inventory also includes several nearby galaxies, galaxy groups, and galaxy clusters. Although these systems are located many millions of light-years away, if the strength of the technology signatures follows an approximate power-law distribution (as transmitters do here on Earth), there could be some rare but very bright signals that are detectable.

“The Breakthrough Listen program is also targeting 100 nearby galaxies, but in the future we will look specifically at large concentrations of stars at cosmological distances to further investigate for very bright and very rare technology signatures,” says Andrew Siemion. it’s a statement.

Nearby galaxies, galaxy groups, and galaxy clusters are a great place to look for these rare and powerful signals, as these systems contain hundreds of billions of stars, many of which will host potentially habitable planets. Since the original Breakthrough Listen surveys did not detect any technology firms, Garrett & Siemion were able to impose restrictions on the luminosity function of possible extraterrestrial transmitters and the limits on the prevalence of very powerful transmitters associated with the billions of stars that make up these systems were also determined. .

For some time, Garrett has been concerned that previous SETI surveys have not taken into account the fact that a radio telescope’s field of view also includes many distant background objects in addition to the nearby target star; he believes that “SETI radio soundings impose stronger limits on the dominance of extraterrestrial intelligence in the Universe distant than is often fully appreciated.

The study has been accepted for publication in Monthly Notices of the Royal Astronomical Society.