HW #9: Stellar Evolution

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Astronomy Assignment #9: Stellar Evolution I
Your Name______________________________________
Your Class Meeting Time __________________________
This assignment is due on __________________________
Submit this cover sheet with your assignment.
Complete the assigned problems from the text listed below and address the Instructor Assigned Topic. Mathematical
problems may be hand written. Write out the problem, show your work in solving the problem and state your answer in
a complete sentence. Failure to complete all three of these tasks will result in less than full credit awarded. The
Instructor assigned topic must be typed.
Review Questions from the first half of Chapter 13: Lives and Deaths of Stars
1. What fundamental property of stars determines their evolution?
2. Why do massive stars last for a short time as main sequence stars but low-mass stars last a long time in the main
sequence stage?
3. How can you detect protostars if the surrounding gas and dust blocks visible light?
4. How do T-Tauri stars get rid of the surrounding gas and dust from which they formed?
5. What is happening in the core of a main sequence star and why is it so stable?
6. What happens to a main sequence star that has stopped fusing hydrogen in its core?
7. Are all red giants or supergiants very massive stars? Why are red giants so big and red? What is going on inside
the giants?
8. What is the evolution sequence for stars around the mass of our Sun? How long is the Sun's main sequence
lifetime?
Instructor Assigned Topic
Complete an evolutionary track for the Sun on the blank HR diagram attached using the data in the table attached.
Label each section of the sun’s post-main sequence evolutionary track with the sun’s current method of energy
production as well as the name of the phase at the endpoint of each segment.
Post-Main Sequence Evolution of the Sun
Stage
Energy
Production
Method
Main
Sequence
Core
Hydrogen
Burning
Red Giant
Shell
Hydrogen
Burning
Horizontal
Branch
Core
Helium
Burning
Red Super
Giant
Shell
Helium
Burning
Planetary
Nebula
None
3,000 K
White
Dwarf
None
50,000 K
Spectral
Type
M
G2
+4.8
(1 L)
M3
-3.6
(2,350
L)
K1
0
(100 L)
M3
-3.9
(3,000
L)
Surface
Temperature
Radius
in Solar
Radii
Core
Temperature
Lifetime
15 Million K
10
Billion
Years
166
50 Million K
100
Million
Years
5,000 K
10
200 Million
K
50
Million
Years
3,000 K
180
250 Million
K
10,000
years
300 Million
K
Short
100 Million
K
Very
Long
5,800 K
3,500 K
1
0.01
2
HR Diagram
30,000 K
-10
9,500 K
7,200 K
6,000 K
5,250 K
3,800 K
1,000 R
60 M
-5
17.5 M
100 R
Absolute Magnitude
5.9 M
2.9 M
0
1.8 M
10 R
1.2 M
0.1 R
1.0 M
5
Sun
.67 M
1 R
0.01 R
10
.21 M
0.001 R
15
20
O
B
A
F
G
K
M
Spectral Type
3
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