Disk vs. Halo Orbits
The Disk Component
Stars, gas, and dust
The spiral arms
Size:
Luminous Diameter ~ 25 kpc
Thickness 300 pc – 1 kpc
O stars and dust smaller
Sun-like stars greater
The Spherical Component
Old Stars, but little gas or dust
The Halo
Globular clusters
Isolated old stars
» red dwarfs, giants, white
dwarfs
The Nuclear Bulge