Extrasolar planets

Abstract

AS Recently as five years ago, the search for planetary systems beyond our own was the subject of a few painstaking surveys by a small but dedicated band of planet-hunters. Their goal was to find extrasolar counterparts of our own giant Jupiter, which circles the Sun once every 11 years. To do this they relied on the fact that the star around which any planet orbits also moves: for instance, the Sun circles its common centre of gravity with Jupiter at the leisurely pace of 12 metres per second. The aim of these early programmes therefore, was to develop techniques that could detect the periodic changes in the Doppler shift of the light from a star as it wobbled back and forth in response to the gravitational tug of an unseen Jupiter-like companion (figure 1).