Astronomy Assignment #4: Stellar Evolution
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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. Define an OB Association and an HII region and describe the relationship between the two.
6. What is happening in the core of a main sequence star and why is it so stable?
7. How does the luminosity and temperature of a star change while it is on the main sequence?
8. What is the “Faint Young Sun” paradox? How has it been resolved?
9. How do astronomers know the mass of stars?
10. What are the types of binary stars and how are they different from each other?
11. Three binary star systems are listed below. What are the masses of each of the six stars? Show your work.
Binary
Star
System
A
B
C
Spectral Types
Orbital Period,
yrs
G2V & K0V
K0V & K5V
M2III & K5V
80
88.3
10,180
Orbital Semimajor axis,
AU
24
23
650
12. What happens to a main sequence star that has stopped fusing hydrogen in its core?
13. Are all red giants or supergiants very massive stars? Why are red giants so big and red? What is going on inside
the giants?
14. If Giant stars are numerically so rare in the galaxy due to their short lifetimes, how is that over half the bright
stars in the night sky are giant stars?
15. What is the evolution sequence for stars around the mass of our Sun? How long is the Sun's main sequence
lifetime?
16. What are the mechanisms of energy production that the Sun will utilize over its lifetime? What stage of stellar
evolution is associated with each (e.g. core H-burning occurs in Main Sequence Stars)?
17. What is a planetary nebula? What are its typical dimensions and lifetime?
18. What is a white dwarf stellar remnant? What is its typical dimensions, temperature and lifetime?
19. What are Type II Supernova? What types of stars experience a Type II Supernova?
20. What is the interior of a star like just before the Type II Supernova?
21. Why are Type II Supernova important for the chemical evolution of the Universe?
22. What do astronomers use Type II Supernova’s for?
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.
2
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
3
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
4