Free Astronomy Magazine July-August 2021

29 JULY-AUGUST 2021 ASTRO PUBLISHING I chnoscale (relative footprint of a given technosigna- ture in units of cur- rent Earth technol- ogy) vs number of targets for several possible technosig- natures. Filled (empty) circles rep- resent continuous (discontinuous) ob- servables. [Hector Socas-Navarro et al. − TechnoClimes 2020] the development of the Break- through Starshot project. Some participants in TechnoClimes 2020 have put on a Cartesian plan the number of possible targets where to look for twelve different types of technosignatures and the related ichnoscale. From the result- ing graph we can see that most of the technosignatures are expected in a limited number of targets and within relatively contained ichno- scale values. Since we can reasonably expect civilizations with low ichno- scale to be more abundant, it is no coincidence that the technosigna- tures most accessible to us appear in the lower part of the graph (where we could place ourselves). Technosignatures of the most abun- dant targets, those represented on the right side of the graph, may seem the most obvious to look for. In reality, our current instrumenta- tion is unsuitable for providing a precise localization (spatial resolu- tion) of artificial infrared sources (Galactic and Dyson spheres). Better it could go with laser signal record- ing (Laser), which however could be discontinuous or occasional. For now, technosigna- tures requiring a di- rect characterization of exoplanets (Lights, Transit shade, Transit CEB) are also beyond our reach. Six technosignatures with the lowest ich- noscale value remain, two of which (Inter- cept and Radio) are however very unpre- dictable. Among the remaining four tech- nosignatures, three (UHR anomaly, NEO, Asteroid pol) concern the possibility of dis- covering artifacts of extraterrestrial origin on asteroids and the Moon, while the last one (Atmos) is the technosignature that we can most realisti- cally hope to discover in the near future, that means traces of artificial pollutants in the atmosphere of a terrestrial planet, evidence of indus- trial or engineering activities. But let’s go back to the three previ- ous technosignatures, those that at first glance seem the most fanciful and that contemplate the possibility H ector Socas-Navarro, physicist at the Instituto de Astrofísica de Canarias, is the main creator of the scale that parameterizes the technosignatures. [IAC]