Milli-arcsecond binaries

As part of an astrometric program (see Loinard et al. in this volume), we have obtained an unprecedented sample of high-resolution (~ 1 mas) VLBA images of several nearby young stellar systems. As was to be expected, these images revealed interesting new characteristics of these objects. Perhaps the most interesting of these characteristics is the detection of a high rate of very tight binary stars (separations of a few mas) in our sample: of the 9 objects observed to date, 5 are binaries of this type.