Ch 10-03 Stellar Clusters

• Recall the Jeans mass.
  Open clusters
  Globular clusters
  
  
  
  [NGC 104 (47 Tucanae), about 700,000 stars within a 18-pc radius]
  
  
• Age of clusters
  
  
  
  
• Distance to clusters
  
  
  [The moving cluster method does NOT rely on the parallax measurement, but requires a measurable proper motion with noticeable convergence. There are very few such applications.]
  
  
  [The main-sequence fitting]
  
  
• Stellar populations
  
  
  
  Metal rich (mass fraction ~ 0.02): Population I, younger (the 2nd generation); open clusters
  Metal poor (mass fraction ~ 0.001): Population II, older (the 1st generation); globular clusters