Stellar Populations
Stellar
Population
Location
Star
motions
Ages of
stars
Brightest
stars
Supernovae
Star
clusters
Association
with gas and dust?
Active star
formation?
Abundance
of heavy elements (mass)
Population
I
Disk and
spiral arms
Circular,
low velocity
Some <
100 million years
Blue giants
Core
collapse (Type II)
Open (e.g.,
Pleiades)
Yes
Yes
2%
Population
II
Bulge and
halo
Random,
high velocity
Only >
10 billion years
Red giants
White dwarf
explosions (Type I)
Globular
(e.g., M3)
No
No
0.1 - 1%
Population II stars are old and metal poor, found in
large orbits in a random spherical distribution.
Population I
stars are young and metal rich (including hot stars), all orbiting in the
disk in the same direction.