Milky Way Galaxy

This diagram shows the major features of our Milky Way galaxy as viewed from the side.  Viewed from above, the galactic disk is shaped like a pinwheel, with a central bulge.  About 150 globular clusters are scattered in a sphere, forming a halo.  Shapley assumed that the halo surrounded the center of the galaxy.  By plotting distances to each cluster he was able to establish the center locate the Sun.  The result was that the Sun and its family of planets, including Earth, are located in the disk about two thirds of the way from the galactic center.