Constraints on extragalactic transmitters via Breakthrough Listen

Abstract

The Breakthrough Listen Initiative has embarked on a comprehensive SETI survey of nearby stars in the Milky Way that is vastly superior to previous efforts as measured by a wide range of different metrics. SETI surveys traditionally ignore the fact that they are sensitive to many background objects, in addition to the foreground target star. In order to better appreciate and exploit the presence of extragalactic objects in the field of view, the Aladin sky atlas and NED were employed to make a rudimentary census of extragalactic objects that were serendipitously observed with the 100-m Greenbank telescope observing at 1.1-1.9 GHz. For 469 target fields (assuming a FWHM radial field-of-view of 4.2 arcminutes), NED identified a grand total of 143024 extragalactic objects, including various astrophysical exotica e.g. AGN of various type, radio galaxies, interacting galaxies, and one confirmed gravitational lens system. Several nearby galaxies, galaxy groups and galaxy clusters are identified, permitting the parameter space probed by SETI surveys to be significantly extended. Constraints are placed on the luminosity function of potential extraterrestrial transmitters assuming it follows a simple power-law and limits on the prevalence of very powerful extraterrestrial transmitters associated with these vast stellar systems are also determined. It is demonstrated that the recent Breakthrough Listen Initiative, and indeed many previous SETI radio surveys, place stronger limits on the prevalence of extraterrestrial intelligence in the distant Universe than is often fully appreciated.

The Breakthrough Listen Search for Intelligent Life: Technosignature Search of 97 Nearby Galaxies

“…Only the results for this work, here shown as six-pointed stars, are corrected for turboSETI noise calculation methods and calculated using an S/N of 33 rather than an S/N of 10. We note that the results of all other studies conducted with turboSETI(Enriquez et al 2017;Price et al 2020;Garrett & Siemion 2022;Uno et al 2023) also represent searches off by a factor of ∼3.…”

“…Surveys within the Milky Way can be specifically designed to capture large numbers of stars by targeting regions of high stellar density (Tremblay & Tingay 2020;Gajjar et al 2021), and Gray & Mooley (2017) observed the galaxies M31 and M33 at 21 cm using the Jansky Very Large Array (VLA) with <1 kHz spectral resolution, sampling ∼10 12 stars and establishing one of the deepest constraints on the luminosity function of extraterrestrial transmitters in the Local Group. Garrett & Siemion (2022) and Uno et al (2023) applied a similar analysis to identify serendipitous observations of extragalactic objects in GBT data. Their analyses of galaxies identified in those fields sampled ∼10 11 and more than 10 13 stars, respectively, with a spectral resolution of 3 Hz, though the greater average distance of their galaxy targets leads to correspondingly higher power requirements and lower sensitivity than the search of nearby galaxies that we present here.…”

UAP Research in Germany: Single Case Studies, Data Management, Understanding of “Strangeness”

“…Zwar machen die Radiowellen-SETI-Projekte inzwischen große Fortschritte (Enriquez et al, 2017;Franz et al, 2022;Gajjar et al, 2021;Garrett & Siemion, 2023;Harp et al, 2016Harp et al, , 2019Ma, P. X., 2023Price et al, 2020;Sheikh et al, 2020;Suresh et al, 2023;Tao et al, 2022;Wlodarczyk-Sroka et al, 2020;Zhang et al, 2020). Doch um mit der gegenwärtigen Empfindlichkeit (10 -26 Watt pro Quadratmeter in einem 1-Hertz-Kanal) beispielsweise Signale von einem 200 Lichtjahre fernen Planeten zu empfangen, müsste der potenziell detektierbare Sender eine Leistung von 10 13 bis 10 15 Watt haben.…”