Astrometric Detection and Investigation of Planetary Systems with the VLT Interferometer

Abstract

The VLT Interferometer is capable of doing astrometry with ~ 10 mi-croarcsecond precision over fields of a few arcseconds by measuring the differential delay between the target star and a (possibly faint) reference object in the K band. With this precision, it is possible to detect planets through the reflex motion of the central star at considerable distance; Jupiter could be found out to ~ 1 kpc. The masses of any planets detected can be determined, independently of the inclination of the orbit. In a “key program”, which would use about 300 observing nights over 10 years on VISA (1.8 m telescopes only), 200 stars could be observed, with 20 to 30 measurements for each star. As a result of this program, an inventory of giant planets around stars of various spectral types could be obtained, including the multiplicity and mass function of the planets. Smaller planets (down to ~ 10 Earth masses) could be found around a few nearby stars. Inclusion of pre-main-sequence objects in the target list would give additional information about the formation of planetary systems.