Mapping Spiral Structure on the far side of the Milky Way [GA]

Little is known about the portion of the Milky Way lying beyond the Galactic center at distances of more than 9 kilo-parsec from the Sun. These regions are opaque at optical wavelengths due to absorption by interstellar dust, and distances are very large and hard to measure. We report a direct trigonometric parallax distance of 20.4_{-2.2}^{+2.8} kilo-parsec obtained with the Very Long Baseline Array to a water maser source in a region of active star formation. These measurements allow us to shed light on Galactic spiral structure by locating the Scutum-Centaurus spiral arm as it passes through the far side of the Milky Way, and to validate a kinematic method for determining distances in this region based on transverse motions.

Read this paper on arXiv…

A. Sanna, M. Reid, T. Dame, et. al.
Thu, 19 Oct 17

Comments: 21 pages, 5 figures, 4 tables, published in Science, October 13 issue