It has a mass of around 1012 solar masses, much of which is dark matter in the halo surrounding the galaxy.
As a barred spiral galaxy, with a Hubble classification of Sbc (spiral arms medium-loosely bound), the milky way is made up of a central bar as well as multiply spiral arms. The four arms, as well as the central bar, are the:
- Milky Way Bar (containing the supermassive black hole at the galactic core, Sagittarius A*)
- Perseus Arm
- Norma/Outer Arm
- Scutum-Centaurus Arm
- Carina-Sagittarius Arm
There are also multiple minor arms, branching off existing arms as spurs, including the: