Figure 13-11 RIVUXG Stellar Populations: Disk Versus Central Bulge This illustration shows the Milky Way Galaxy’s inner and outer halos. A halo is a spherical cloud of stars surrounding a galaxy and contains similar stars. In contrast, the disk and central bulge of the Milky Way contain different populations of star types. Population I stars, of which the Sun is an example, are found in the disk. The inner and outer halos only contain older Population II stars. The central bulge contains both types, but many more red stars than blue stars.