Origin of Galaxy

• Theory must explain

  • Age of oldest star clusters
    • 7 billion yrs open clusters
    • 11-17 billion yrs globular clusters
  • Two distinct populations:
    • Disk: younger, more heavy elements
    • Sphere: older, fewer heavy elements
  • Orbits of populations:
    • Disk: circular orbits confined to plane, in a single direction
    • Sphere: random orbits

Notes: