Although rare, transition disks may end up playing a crucial role in our understanding of the planet formation process. These disks are otherwise similar to regular accretion disks, except their central regions contain significantly less (or different) dust. The original dust content in those regions may have been accumulated into the larger bodies of a newly-formed planetary system, or perhaps otherwise dispersed. While we cannot yet directly detect any such planets in these systems, we may be able to infer some of their properties based on how they have affected the remaining disk material.
Our group has been using the SMA interferometer in its highest angular resolution configuration to image the diminished 870 micron dust emission from the central cavities of these transition disks. Those data provide direct measurements of the cavity sizes, which we find can range from 20-40 AU in radius in some cases, comparable to the orbital dimensions of planets in our Solar System. For more details, see our recent articles about the GM Aurigae disk or other transition disks in Ophiuchus. Or, you can find a recent popular article about our work on these disks in the Sky & Telescope magazine.
