Abstract

In the last decade or so, it has become possible to measure the distance and the velocity vector of young stars located within 500 pc of the Sun with an accuracy of order 1% using Very Long Baseline Interferometry (VLBI) techniques. This represents an improvement by more than 1 order of magnitude over what was previously possible, and opens the door to some extremely high accuracy astrophysics. In particular, theoretical pre-main sequence stellar evolutionary models can now be confronted with very accurate observational constraints. The space distribution, and the internal structure and kinematics of star-forming regions, can also be investigated in unprecedented detail. This has important consequences both for star formation and for Galactic structure studies. In this talk, I will present the first results of the Gould's Belt Distances Survey (GOBELINS): a large project to measure the distances to the five most prominent nearby regions of star-formation using the VLBA. In particular, I will focus on Ophiuchus, Serpens and Orion, providing mean distances, internal kinematics, depth constraints, and internal kinematics information for each. I will also describe how many of the targets detected with the VLBA happen to be young multiple systems, and how the combination of the VLBA astrometry and NIR spectroscopy and astrometry can yield extremely accurate masses for these systems.