I will describe several ongoing or recently-completed observational programs to study young stars with a range of high-resolution imaging techniques, including laser guide star adaptive optics imaging, nonredundant aperture-mask interferometry, and deep seeing-limited imaging. My results indicate that many of our previous ideas about multiplicity and planet formation were incorrect or incomplete. The primordial binary star population for solar-type stars appears significantly different from the field population, and the mass dependence of binary properties is even more pronounced than had been previously appreciated. I am also placing significant constraints on the frequency and properties of giant planets in outer solar systems (a=5-40 AU). This indicates either that the population parameters (frequency and separation/mass functions) suggested by RV surveys are wrong, or that the expected fluxes are indeed fainter than older models predicted. Finally, I have found that close stellar companions can significantly influence the evolution and lifetime of protoplanetary disks. Some of the "transitional disks" (disks with gaps or inner holes) that have been suggested as sites of ongoing planet formation are instead being cleared by close binary companions, and most of the youngest (<2 Myr) stars without disks appear to be close binary systems where this clearing process has already finished.



More information on Dr. Kraus can be found on his website: http://www.astro.caltech.edu/~alk/