| Population I | Population II | |
| Age | Young to Old (106-109 years) |
All Old (1010) years |
| Star Temperature | Generally Blue (hot) | Red (cooler) |
| Location | Disk, concentrated in Spiral Arms | Halo and Bulge |
| Orbits | Clockwise and circular in Disk | All directions, plunging through Disk |
| Metals | Lots of Metals (like Sun) | Low Metal Abundance |
| Supernova | Type II & Type I | Type I ONLY |
| Examples | OB Clusters, T Tauri stars | Globular Clusters, Metal Poor old stars |
Recall the Stellar Clusters:
Open Clusters are loosely scattered clusters of stars found in the Disk. They are
Pop I stars,
as they follow the Disk kinematics (motions) and have rather high amounts of metals in them.
They can
contain as massive as O & B stars, or can be a bit older, with the most massive stars being
A stars.
Globular Clusters are very TIGHTLY bound clusters, found in the Halo or plunging
in toward the
nucleus of the galaxy. They are all very old. The hottest main sequence stars are cooler
than our Sun.
Because they were among the first stars to form, they have few metals. These are Pop II
stars
Associations are much larger, loose collections of very young stars, usually O & B stars (OB Associations), as well as lower mass stars. They are found close to the gas they formed from, along the spiral arms. You also find T Tauri stars (young low mass stars, T Associations).