1. Astronomy 105 Laboratory
Lab 09

2. Ages and Distances to Clusters
Lab 09
Ages and Distances to Clusters

3. Night Lab One additional night lab will be added to calendar
First clear night
Monday, November 6
Tuesday, November 7
Wednesday, November 8
Thursday, November 9

4. Stellar Main-sequence Lifetime
Stellar Birth
Massive stars form quickly
Low mass stars form slowly
Main-sequence Stars
Fuse hydrogen in their cores
High mass stars
consume hydrogen at a furious rate
high luminosities
short lifetimes
Low mass stars
consume hydrogen at a low rate
low luminosities
long lifetimes
Giant Stars
Core hydrogen exhausted

5. Main-Sequence Lifetimes

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

7. Star clusters help us test models of stellar evolution because they contain stars of same age but at different life stages
Star_cluster_evolving.swf
Massive blue stars leave the main-sequence first, followed by white, yellow,
orange, and red stars

8. Pleiades - Open Cluster B6 stars -- 100 million yrs. MS lifetime
Distance ly Age million years
B6 stars million yrs. MS lifetime
age of cluster = lifetime of stars at main-sequence turnoff point

9. standard main-sequence G stars -- 10 billion yrs. MS lifetime
M3 - Globular Cluster
distance - 32,000 ly age - 10 billion years old
standard main-sequence
G stars billion yrs. MS lifetime
age of cluster = lifetime of stars at main-sequence turnoff point

11. Interstellar Dust Reddens Light (makes stars appear cooler)
Dims Light (makes stars appear further away)
Interstellar Reddening

12. Important: Do not write or mark on the Cluster Handout

13. M45

14. D.M. = 5.7

15. M45
5.7

16. M45
5.7
130
Distance = 130 pc
D.M. = 5.7

17. Color Excess =

18. M45
5.7
130
0.05
0.15
5.55
120
391

19. Color of Turn-off Point = - 0.01

20. M45
5.7
130
0.05
0.15
5.55
120
391
-0.01

21. Color of Turn-off Point = - 0.01
M45
5.7
130
0.05
0.15
5.55
129
420
-0.01
Age = 1 X 108 years
1x108
Color of Turn-off Point =

22. M45
5.7
130
0.05
0.15
5.55
120
391
-0.01
1x108

23. The End