The Milky Way is the galaxy where our Solar System is located. It consists of baryonic matter (stars, gas, and dust), but mainly of dark matter that is gravitationally bound to the baryonic matter.
The Milky Way (MW) is a spiral galaxy with an approximate mass of 1012 M⊙, where roughly 6 × 1010 M⊙ is baryonic matter, distributed in three main components: disk, stellar halo, and bulge; all of them centered at the center of the MW.
The disk is a flat rotating structure formed by stars, gas, and dust. It is where the star-forming regions are located, and the young stars form a spiral structure. The spiral arms (S shaped) are bright relative to the disk, and they inspired the name of spiral galaxy. The disk mass is approximately 80 % of the total baryonic mass of the Milky Way, and its diameter is 50 kpc. The stars on the disk have metallicities (abundances of elements heavier than He) larger than one tenth of the solar value, and the stars are younger than 10 Gyr. At...