The position of β Pictoris b position relative to the debris disk

Abstract

Context. We detected in 2009 a giant, close-by planet orbiting β Pic, a young star surrounded by a disk that has been extensively studied for more than 20 years. We showed that if the planet were located on an inclined orbit, this could account for several peculiarities of the β Pictoris system. However, the available data did not permit us to measure the inclination of β Pic b with respect to the disk, and in particular to establish in which component of the disk-either the main, extended disk or the inner inclined component/disk-the planet was located. Comparison between the observed planet position and the disk orientation measured using previous imaging data was not an option because of potential biases in the measurements. Aims. Our aim is to measure precisely the planet location with respect to the dust disk using a single high-resolution image, and correcting for systematics or errors that degrade the precision of the disk and planet relative-position measurements. Methods. We gathered new NaCo data in the Ks band, with a set-up optimized to derive simultaneously the orientation(s) of the disk(s) and the planet projected position. Results. We show that the projected position of β Pic b is above the midplane of the main disk. With the current data and knowledge of the system, this implies that β Pic b cannot be located in the main disk. The data instead suggest that the planet is located in the inclined component. © 2012 ESO.