Letter to the Editor

A probable giant planet imaged in the β Pictoris disk^*

VLT/NaCo deep L'-band imaging

¹ Laboratoire d'Astrophysique de l'Observatoire de Grenoble, Université Joseph Fourier, CNRS (UMR 5571), BP 53, 38041 Grenoble, France e-mail: anne-marie.lagrange@obs.ujf-grenoble.fr
² Laboratoire d'Études Spatiales et d'Instrumentation en Astrophysique, Observatoire de Paris, CNRS (UMR 8109), Université Pierre et Marie Curie, Université Paris-Diderot, 5 place Jules Janssen, 92190 Meudon, France
³ Office National d'Études et de Recherches Aérospatiales, 29 avenue de la Division Leclerc, 92322 Châtillon, France
⁴ Centre de Recherche Astronomique de Lyon, CNRS (UMR 5574), Université Claude Bernard, École Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 7, France

Received: 10 November 2008
Accepted: 18 November 2008

Abstract

Context. Since the discovery of its dusty disk in 1984, β Pictoris has become the prototype of young early-type planetary systems, and there are now various indications that a massive Jovian planet is orbiting the star at ~10 AU. However, no planets have been detected around this star so far.

Aims. Our goal was to investigate the close environment of β Pic, searching for planetary companion(s).

Methods. Deep adaptive-optics L'-band images of β Pic were recorded using the NaCo instrument at the Very Large Telescope.

Results. A faint point-like signal is detected at a projected distance of 8 AU from the star, within the northeastern extension of the dust disk. Various tests were made to rule out possible instrumental or atmospheric artefacts at a good confidence level. The probability of a foreground or background contaminant is extremely low, based in addition on the analysis of previous deep HST images. Its apparent magnitude would indicate a typical temperature of ~1500 K and a mass of ~8 M_Jup. If confirmed, it could explain the main morphological and dynamical peculiarities of the β Pic system. The present detection is unique among A-stars by the proximity of the resolved planet to its parent star. Its closeness and location inside the β Pic disk suggest a formation process by core accretion or disk instabilities rather than binary-like formation processes.