RADIAL-VELOCITY SEARCHES FOR OTHER PLANETARY SYSTEMS - CURRENT STATUSAND FUTURE-PROSPECTS

Measurement of variations in the radial velocities of stars due to the reflex orbital motion of the star around the planetary-system barycen ter constitutes a powerful method of searching for substellar or plane tary mass companions. After several years of patient data acquisition, radial-velocity searches for planetary systems around other stars are now beginning to bear fruit. In late 1995 and early 1996, three candi date systems were announced with Jovian-mass planets around solar-type stars. The current paradigm for low-mass star formation suggests that planetary systems should be able to form in the circumstellar disks s urrounding young stellar objects. These newly discovered systems, and other discoveries which will soon follow them, will test critically ou r understanding of the processes of star- and planet-formation. We rev iew the techniques used in these radial-velocity searches and their re sults to date. We then discuss planned improvements in the surveys, an d the prospects for the next 20 years.