The search for extrasolar planets (EXOPLANETS) is one of the most rapidly expanding fields in astrophysics. Thanks to recent space-based efforts the number of detected planets in extrasolar stellar systems has increased dramatically, and more than 900 objects have been identified as of today, see e.g. http://exoplanet.eu/catalog/. With candidates identified in the so-called habitable zone (HZ)1 the question of extraterrestrial life becomes very actual. Here we discuss ideas that could lead to infer the presence (or the past existence) of an extraterrestrial civilization by the detection of artifacts in orbit around the host planet.
The theoretical band around a star where a planet could orbit and host liquid water↩