Published online by Cambridge University Press: 25 May 2016
Many features of the Milky Way appear weird or unique, because of the peculiar point of view. However the same features are observed more easily and clearly in nearby galaxies. The Milky Way appears to cumulate many dynamical features, such as a bar, a nuclear disk, a perpendicular nuclear bar (?), lopsidedness, an inner ring (molecular ring at 5kpc), a peanut-shape bulge, a warp, and a polar ring. By comparison with external galaxies, and also results from N-body simulations, we can infer the most probable bar angular velocity and length, and interpret the ring features.