In spite of much work, the overall spiral structure morphology of the Milky Way remains somewhat uncertain. In the last two decades, accurate distance measurements have provided us with an opportunity to solve this issue. Using the precise locations of very young objects, for the first time, we propose that our galaxy has a multiple-arm morphology that consists of two-arm symmetry (the Perseus and Norma Arms) in the inner parts and that extends to the outer parts, where there are several long, irregular arms (the Centaurus, Sagittarius, Carina, Outer, and Local Arms).

Cone search capability for table J/ApJ/947/54/table1 (The astrometric parameters of high-mass star-forming region (HMSFR) masers)

Cone search capability for table J/ApJ/947/54/tableb1 (The properties of the external MW-like galaxies; see Appendix B)