Astronomy 120
HOMEWORK - Chapter 20
Stellar Evolution
Use a calculator whenever necessary.
For full credit, always show your work and explain how you got your answer in full, complete sentences on a separate sheet of paper.
Be careful about units!
Please CIRCLE or put a box around your final answer if it is numerical.
If you wish, you may discuss the questions with friends, but please turn in your own hand-written solutions, with questions answered in your own way.
1. Chaisson Review and Discussion 20.2
How do astronomers test the theory of stellar evolution?
2. Chaisson Review and Discussion 20.4
Why is the depletion of hydrogen in the core of a star such an important event?
3. Chaisson Review and Discussion 20.5
What makes an ordinary star become a red giant?
4. Chaisson Review and Discussion 20.6
Roughly how big (in A.U.) will the Sun become when it enters the red-giant phase?
5. Chaisson Review and Discussion 20.8
Do all stars eventually fuse helium in their cores?
6. Chaisson Review and Discussion 20.9
What is a helium flash?
7. Chaisson Review and Discussion 20.11
How do the late evolutionary stages of high-mass stars differ from those of low-mass stars?
8. Chaisson Review and Discussion 20.12
What is the internal structure of a star on the asymptotic-giant branch?
9. Chaisson Review and Discussion 20.13
What is a planetary nebula? Why do many planetary nebulae appear as rings?
10. Chaisson Review and Discussion 20.14
What are white dwarfs? What is their ultimate fate?
11. Chaisson Review and Discussion 20.18
How can astronomers measure the age of a star cluster?
12. Chaisson Review and Discussion 20.19
What are the Roche lobes of a binary system?
13. Chaisson Problem 20.2
Use the radius-luminosity-temperature relation to calculate the radius of a red supergiant with temperature 3000 K (half the solar value) and total luminosity 10,000 times that of the Sun. How many planets of our solar system would this star engulf?
14. Chaisson Problem 20.3
What would be the luminosity of the Sun if its surface temperature were 3000 K and its radius were…
a) 1 A.U.?
b) 5 A.U.?