| Population I | Population II | |||
| Extreme | Intermediate | Intermediate | Extreme | |
| Location | spiral arms | disk | bulge | halo |
| Metals (%) | 3 | 1.6 | 0.8 | less than 0.8 |
| Shape of orbit (see below) |
circular, in galactic plane | slightly elliptical in galactic plane | moderately elliptical, extending out of galactic plane | highly elliptical, not confined to galactic plane |
| Average age (yr) | 100 million and younger | 0.2-10 billion | 2-10 billion | 10-14 billion |
