2009ApJ...694..192M

We have used the Very Long Baseline Array to measure the annual parallax of the H₂ O masers in the star-forming region IRAS 00420+5530. This measurement yields a direct distance estimate of 2.17±0.05 kpc (an error of less than 3%), which disagrees substantially with the standard kinematic distance estimate of ∼4.6 kpc (according to the rotation curve of Brand & Blitz), as well as most of the broad range of distances (1.7-7.7 kpc) used in various astrophysical analyses in the literature. The three-dimensional space velocity of IRAS 00420+5530 at this new, more accurate distance implies a substantial noncircular and anomalously slow Galactic orbit, consistent with similar observations of W3(OH) (Xu et al. and Hachisuka et al.), as well as line-of-sight velocity residuals in the rotation curve analysis of Brand & Blitz. The Perseus spiral arm of the Galaxy is thus more than a factor of 2 closer than previously presumed, and exhibits motions substantially at odds with axisymmetric models of the rotating Galaxy.