A probable giant planet imaged in the β Pictoris disk VLT/NaCo deep L′-band imaging

Context. Since the discovery of its dusty disk in 1984. beta 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 similar to 10 AU. However, no planets have been detected around this star so far. Aims. Our goal was to investigate the close environment of beta Pic, searching for planetary companion(s). Methods. Deep adaptive-optics L'-band images of beta 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 similar or equal to 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 L' = 11.2 apparent magnitude would indicate a typical temperature of similar to 1500 K and a mass of similar to 8 M-Jup. If confirmed, it could explain the main morphological and dynamical peculiarities of the beta 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 beta Pic disk suggest a formation process by core accretion or disk instabilities rather than binary-like formation processes.