Astronomy Assignment #6: The Sun
Your Name______________________________________
Your Class Meeting Time __________________________
This assignment is due on Tuesday, 19 Nov
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.
Read Chapter 12: Our Sun and Stellar Structure
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Introduction
The Sun--An Average Star
o Size
o Composition
o The Sun's Interior
The Sun's Power Source
First a detailed explanation of why we think nuclear fusion is the energy source and then an outline.
o Solar Luminosity---huge energy output!
o Possible Sources of Energy
o Gravitational Contraction Doesn't Power the Sun Long Enough
o Nuclear Fusion Needs Extreme Temperatures and Densities
o Some Mass is Converted to Energy in Fusion Reactions
o Why Stars Use a Complicated Chain Reaction
o Hydrostatic Equilibrium Controls the Reaction Rates
o Summary
Neutrino
o Description
o Solar Neutrino Problem
o Explorations of Neutrino Detectors
Interior Structure of Stars
o Mathematical Models
1. Temperature
2. Pressure
3. Mass Density
o Equation of State The ideal gas law relates temperature, pressure, and density.
o Gravity Holds a Star Together Hydrostatic Equilibrium
o Other Pieces
1. Continuity of Mass -- conservation of mass
2. Continuity of Energy -- conservation of energy
3. Energy Transport: radiation, convection, conduction
4. Opacity: how well the gas absorbs light
Answer the following Review Questions:
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What are the two main gases in the Sun? How does the Sun's mass and size compare with Jupiter?
What goes on in the core, Envelope (radiative zone, and convection zone) of the Sun?
How does nuclear fusion produce energy?
Why does nuclear fusion need high temperatures and densities?
5. Why is it so hard to develop nuclear fusion as a dependable power source on Earth?
6. Why will chemical reactions or gravitational contraction not work for powering the Sun?
7. What is the net result of the nuclear fusion chain process? Why does nature use the complicated chain process
instead of a one-step fusion procedure?
8. Where are neutrinos produced? What information can they tell you about interior conditions in the Sun?
9. What was the solar neutrino problem? How was the problem solved and what are the implications of that
solution?
10. How can you determine what the interiors of stars are like?
11. What is being equilibrated in hydrostatic equilibrium? How does hydrostatic equilibrium explain why the
temperature and density increases inward toward the core of a star?
12. How does hydrostatic equilibrium control the fusion rate in the Sun?
13. What would happen to the size of a star if its core steadily produced more energy than it did at some earlier time
(e.g., when a main sequence star becomes a red giant)?
14. What would happen to the size of a star if its core steadily produced less energy than it did at some earlier time
(e.g., when a star stops fusing nuclei in its core)?
15. Do photons produced in the core zip right out from the Sun or does it take longer? Explain why.
Instructor Assigned Topic:
1.
Answer the question below following our class lecture on how the Sun produces energy. This identical question will be on
the next exam – so do it correctly now.
Describe how the Sun produces energy by describing the net proton-proton chain, as
presented in class, including the origin of the particles in the net p-p chain reaction.
Include the effect of thermalization on the gamma rays and a summary of the twolayer model of the Sun’s interior.
Grading Rubric:Full credit awarded to responses that address the following points:
1.
The Sun produce energy by nuclear fusion through the Proto-Proton Chain
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a. Details of the reactions as covered in class: 41 H 12 He  2  6
b. Brief discussion of neutrinos
c. Brief discussion of gamma rays including thermalization
Mass Loss is associated with energy production
The Two-Layer Model of the Sun
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