1. Lab 8 – The Distance to the Pleiades

2. Open or Galactic Cluster

3. M13 - Globular Cluster Distance-23,000 ly Size-150 ly

4. Stars in a Cluster Common Properties Distance Age Chemical composition Different Properties Spectral Types (temperature) Luminosity Class (size) Mass

5. D >10 pc 10 pc D <10 pc 10 pc Star Cluster D >10 pc D <10 pc O B A F G K M Main-sequence HR Diagram O B A F G K M Color-Magnitude Diagram Distance Modulus = m - M The difference between the absolute magnitude and the apparent magnitude can be used to find the distance to a star cluster. If m-M > 0 then the distance to the cluster is > 10 pc. If m-M = 0 then the distance to the cluster is = 10 pc. If m-M < 0 then the distance to the cluster is < 10 pc. DM { Distance Modulus

7. n Interstellar Dust –Reddens Light (makes stars appear cooler) –Dims Light (makes stars appear further away)

8. Pleiades - Open Cluster

9. The End.