 Authors invoked a variety of mechanisms for superluminal travel (or generation starships) and placed their stories on worlds in planetary systems around other stars, an innovation that gave them the freedom to construct exotic fictional planets and themes.This tendency became predominant once the exploration of the Solar System was complete enough to conclusively demonstrate the unlikelihood of any highly developed form of extraterrestrial life here, aside from humans on Earth.Although some of the stars named in works of science fiction are purely imaginary, many authors and artists have preferred to use the names of real stars that are well known to astronomers, and indeed the lay public, either because they are notably bright in the sky or because they are relatively close to Earth.