Extra-solar system planets: searches, discoveries and characteristics

Abstract

The study of planets outside our solar system constitutes a new branch of astronomy that literally did not exist a decade ago. This discussion begins with how people have thought about other worlds in the past and some of the reported detections that turned out not to be true. It continues with a brief description of several successful ways of finding exoplanets and the properties of the planets found and their host stars, and concludes with an attempt to look ahead. Most of the planets now known revealed themselves because their mutual orbits with their parent stars impose small, periodic radial velocity shifts in the stellar spectra, and most of the host stars are rich in heavy elements by the standards of the solar neighbourhood. The inventory of actual and potential detection methods has reached about two dozen.