Page 11, The Milky Way and Galaxies: [Last Page] [Next Page] [Lecture Notes] [Class Home Page]

Population I and Population II Stars (cont.)

Comparative Properties of Pop I and Pop II Stars:


	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


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 i n 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 sta rs


Associations are much larger, loose collections of very young stars, usually O & B stars, 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 (youn g low mass stars).