Different studies of the global pitch angle of the Milky Way's spiral arms

There are many published values for the pitch angle of individual spiral arms, and their wide distribution (from −3° to −28°) begs for various attempts for a single value. Each of four statistical methods used here yields a mean pitch angle in a small range, between −12° and −14° (Table 7, Fig. 2). The final result of our meta-analysis yields a mean global pitch angle in the Milky Way's spiral arms of −13.1° ± 0.6°.