One reason for this is differential rotation of the galaxy, which we will meet later. Our Sun was probably a member of a cluster when it was young, but we cannot identify any of its siblings now. The Milky Way is the name given to our own galaxy. In this section we are going to try to understand how stars and other material are distributed around the sky. We see the Milky Way as a band of light in the sky.
Closer inspection shows it to be made up of lots of individual stars .
The Milky Way is actually a disk galaxy. We do not have an accurate map of the Galaxy, but guess that it would look similar to other galaxies , that we have seen, if viewed from outside. Note the structure of a disk galaxy. Most of the interstellar matter in the galaxy is in the disk. The disk is rotating, and contains spiral arms , which are concentrations of stars, gas, and dust.