The Hipparcos observations and the mass of sub-stellar objects

Abstract

The Hipparcos Intermediate Astrometric Data have been used lately to estimate the inclination of the orbital plane of candidate extrasolar planets. Whereas most of these investigations derive almost face-on orbits, we show that the astrometric data are seldom precise enough to undertake such studies and that the ``face-on'' result might be just a spurious effect of the method. Based on observations from the Hipparcos astrometric satellite operated by the European Space Agency (ESA 1997).