Stefan Kraus is 2009 Sagan Fellow, researching the effect of planets on protopanetary disk structure. He sends us the following report on his work:

The evolution of protoplanetary disks enters a critical phase once planetary bodies form and start to gravitationally interact with the disk material, causing dust-cleared gaps, disk warps, or co-rotating spiral density patterns. We aim to employ recent technological advancements in infrared interferometry to directly detect these planetary imprints on the disk structure. Interferometers combine the light from more than one telescope to synthesize the resolving power of a much larger aperture (up to 330m in the case of the CHARA array) and can obtain model-independent interferometric images. Some first results using this imaging approach were presented in our recent study on the high-mass young stellar object IRAS13481-6124 (Kraus et al. 2010, Nature 466, 339), where we used the VLT Interferometer detect a hot compact dust disk around this 20 solar mass YSO. In the course of upcoming projects, we aim to apply the same technique to image the protoplanetary disks around Herbig Ae/Be or T Tauri stars with milliarcsecond (sub-AU) resolution. To optimize the resolution and image fidelity, we will employ the CHARA array on Mt. Wilson and new 6-telescope beam combination and fringe tracking instrumentation, which has been developed by our group around John Monnier (Univ. of Michigan) and is currently under commissioning. Ultimately, these imaging techniques should reveal the signatures of planet formation, opening exciting new opportunities for the detection and characterization of extrasolar planets and providing important constraints on their migration properties.