Are we alone in the universe? To answer this question, astronomers have been using a variety of methods in the past decades to search for habitable planets and for the signals from extraterrestrial observers.
The first part of this venture has been highly successful: More than 2,000 planets around distant stars — so called exoplanets — have been found so far. The second part, the search for extraterrestrial intelligence (SETI), has not yet been successful.
Via Dr. Stefan Gruenwald