Possible search for an infant planet by astrometry: Estimation of the effect of protoplanetary disks

Abstract

We examine how circum-stellar disks affect the stellar wobble caused by the planet's gravity. The disk's asymmetry moves not only the position of the mass center of the star-disk-planet system but also the position of the photo-center of the light from the system. The photo-center shift induced by the disk is significant compared to the planet's effect if the planet's mass is as small as Jupiter. However, astrometry using interferometers is not sensitive to the extended disk light, and thus the effect of the disk light is greatly reduced.