A hot compact dust disk around a massive young stellar object

Circumstellar disks are an essential ingredient of the formation1 of low-mass stars. It is unclear, however, whether the accretion-disk paradigm can also account for the formation of stars more massive than about 10 solar masses2, in which strong radiation pressure might halt mass infall3, 4. Massive stars may form by stellar merging5, although more recent theoretical investigations suggest that the radiative-pressure limit may be overcome by considering more complex, non-spherical infall geometries6, 7. Clear observational evidence, such as the detection of compact dusty disks8 around massive young stellar objects, is needed to identify unambiguously the formation mode of the most massive stars. Here we report near-infrared interferometric observations that spatially resolve the astronomical-unit-scale distribution of hot material around a high-mass (~20 solar masses) young stellar object. The image shows an elongated structure with a size of ~13 × 19 astronomical units, consistent with a disk seen at an inclination angle of ~45°. Using geometric and detailed physical models, we found a radial temperature gradient in the disk, with a dust-free region less than 9.5 astronomical units from the star, qualitatively and quantitatively similar to the disks observed in low-mass star formation. Perpendicular to the disk plane we observed a molecular outflow and two bow shocks, indicating that a bipolar outflow emanates from the inner regions of the system.