| Description: | With astrometric VLBI observations we can now reach accuracies at a level of 10 micro-arcseconds. This enables us to measure trigonometric parallaxes and proper motions of high mass star forming regions in the Milky Way out to several kpc with accuracies of a few percent. Using this method, we can trace the spiral arms of the Milky Way and it's rotation curve. First results for 18 star forming regions suggest a significant higher rotation speed of the Milky Way, and that massive star forming regions rotate on average slower than the Milky Way. The recently started BeSSeL (Bar and Spiral Structure Legacy) Survey, a VLBA key science project, will be introduced.
Shown are all the sources measured so far (green) with their error bars, and the first year sources from the BeSSeL Survey (blue). |
