1. Properties of Stars
Chapter 16

2. Fig. 16.1
1 parsec = 3.26 light years

3. Fig. 16.2

4. Fig. 16.4

5. Fig. 16.6

6. Fig. 16.7

7. Fig. 16.8

8. Fig. 16.9

9. Fig

10. Fig

11. Fig

12. Fig

13. Fig

14. Fig

15. Fig

16. Fig

17. Fig

18. Fig
Hertzsprung
-Russell

19. Fig

20. Fig

21. Tab. 16.1

22. Tab. 16.2

23. Summary Q: How do we know what elements are on a star?
A: We analyze the light coming from the star and we see descrete
spectral lines (colors) of definite color and energy.
The correct sequence of these lines and of their energy looks
form a “staircase” which is used as the fingerprint of
each element, because it is unique to that particular atom that
emits it, and works as a “barcode” that tells us which
element emits this light.
Q: What is the reason for this “staircase”?
A: The reason for this “staircase” is the quantization of the
possible levels (states) the electron can be in a given atom.
Namely, the electron in the atom cannot be in any energy
level but in very precisely defined energy levels, like a
“staircase” where you can only be at a specific step and not
in-between steps.
Different atoms have different charge in their nucleus which
exerts different force on the electron and therefore the energy
levels of a particular atomic “staircase” is specific to the
particular atom.