Institute for Advanced Study Astrophysics Seminar

The Bar and Spiral Structure Legacy (BeSSeL) Survey is an NRAO Key Science Project that has been awarded 5000 hours of VLBA observing time from 2010 to 2015. Results from the first year's observations will be presented. A major goal is to determine the Milky Way's spiral structure by measuring trigonometric parallaxes and proper motions for hundreds of high-mass star forming regions. Also, with full 3-dimensional spatial and velocity information, we will be able to construct an accurate rotation curve for the Milky Way and estimate the distance to the Galactic center and the circular rotation speed at the Sun to about 1% accuracy.