Abstract

Star and planet formation is one of the most active and exciting research areas of modern astrophysics. Many of the open questions in this field are related to the structure and physics of the innermost regions of protoplanetary discs, where material is transported onto the forming star, ejected in powerful jets & outflows, or accreted onto newly-formed planets.

In this talk I will outline the new opportunities provided by infrared interferometry, which allow us for the first time to resolve the structure & physical processes in the AU-scale inner disc regions. I will discuss near- and mid-infrared interferometric observations on intermediate-mass pre-main-sequence stars that probe the distribution of hot dust grains located at the dust sublimation radius. We find indications for a radial temperature gradient and an increased vertical scale height at the sublimation radius, supporting models of irradiated discs with puffed-up inner rim. Besides constraining the distribution of the continuum-emitting dust, our interferometric observations in spectral lines with high spectral dispersion (R=12,000) probe the kinematics of hot gas that is located in the magnetospheric accretion and outflow-launching region close to the star.

Transitional disc objects are believed to be at a later evolutionary stage and to exhibit a gapped or dust-cleared inner disc structure. Our interferometric observations on these objects constrain the gap geometry and reveal complex density inhomogeneities that might be triggered by orbiting planets.

Finally, I will give an outlook on the upcoming generation of interferometric instruments at the VLT and MRO Interferometer, as well as the “Planet Formation Imager” (PFI) initiative, which aims to develop the roadmap for the construction of a new interferometric facility that will be optimised to unmask all the major stages of planet formation, from initial dust coagulation, gap formation, evolution of transition discs, mass accretion onto planetary embryos, and eventual disc dispersal.