Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way

Understand

We compile and analyze ~200 trigonometric parallaxes and proper motions of molecular masers associated with very young high-mass stars.

• These measurements strongly suggest that the Milky Way is a four-arm spiral.
• Fitting log-periodic spirals to the locations of the masers, allows us to significantly expand our view of the structure of the Milky Way.
• We present an updated model for its spiral structure and incorporate it into our previously published parallax-based distance-estimation program for sources associated with spiral arms.