An updated view of the Milky Way from the BeSSeL programme

While it is known that the Milky Way is a barred spiral galaxy, the precise locations of the spiral arms are not easily derived by observations, because of the Sun's location in the disk plane. The Galactic disk is large (radius of ~15 kpc) and the high dust obscuration in the disk plane limits distances from optical astrometry to a few kpc. The Bar and Spiral Structure Legacy (BeSSeL) programme and the Japanese VERA project measured parallaxes and proper motions, via VLBI maser astrometry, for more than 200 high-mass star-forming regions out to a distance of 20 kpc. BeSSeL has provided a new parametrisation of the spiral arm structure and determined the fundamental Galactic parameters. The BeSSeL results presented here have been published in [1].