The Search for Extrasolar Planets Since the first discovery of a planet around another normal star in 1995 we have known of the existence of extrasolar planets ("exoplanets" for short") - and later also of extrasolar planetary systems - although so far, only giant, Jupiter-like planets have been discovered. By mid-2001, astronomers have found nearly 70 extrasolar planets and at least three other planetary systems with more than one planet. No Earth-like planets found so far The fact that no Earth-like planet has been found until now is above all because of the limitations of current astronomical telescopes and instruments. They are not "sensitive" enough to find smaller, Earth-like planets around foreign stars. The lightest exoplanet found so far weighs about 50 times more than the Earth. However, great efforts are now being made to improve the situation. New, extremely powerful instruments at the largest telescopes on the ground and soon also in space will be able to search for smaller planets around nearby stars. This is a scientific discipline in very rapid development and discoveries are made all the time. Who knows what next week will bring to us? The major websites There are several active groups of scientists working in this field with ground-based telescopes. The latest news may be found at some of the main websites, from where there are also many links to related webpages: The Geneva Extrasolar Planet Serach Programmes The University of California Search For Extrasolar Planets The Extrasolar Planet Encyclopaedia (Paris Observatory) Space mission In addition to ground-based observational programmes, various space missions are also being planned that will search for exoplanets above the disturbing effects of the Earth's atmosphere. The include: ESA's Darwin project The CNES COnvection ROtation and planetary Transits (COROT) The NASA Space Interferometry Mission Key questions The possibility of life around the exoplanetary systems, and how those lifeforms may be different from our own, can be evaluated and investigated with current theoretical models. Maybe we are now close to beginning to grasp little bits and pieces of the answers to some of the related key questions: Is our planetary system a common and/or typical example of the formation and evolution of planets? Are planetary systems a usual result of a stellar birth or are planets rather rare and unusual phenomena? What causes the differences between the planets? What are the possibilities for friendly habitats and the existence of Life elsewhere in the Universe? How does a planetary system evolve around a star?