Free Astronomy Magazine July-August 2021

26 ASTRO PUBLISHING have followed an evolutionary path similar to ours and are hence recog- nizable with the instruments at our disposal. Since there are various forms through which an ETI can reveal itself, astro- biologists looking for technosigna- tures can make use of the databases from many research programs al- ready started with other purposes. For example, the study of exoplan- ets atmospheres in transit in front of their stars can highlight mole- cules that are hardly present in na- ture in certain abundances. After sixty years of fruitless searches for alien signals in the radio domain, many ETI hunters are increasingly T he night lights of an exoplanet akin to the one shown here could be observed from Earth. Similarly, an alien civilization might notice our artificial lights, which on some continents have intensity peaks similar to these. [Techno- Climes 2020]