Objectives/HW

The student will be able to:		HW:
1	Describe the overall structure of the Sun in terms of its core, radiation zone, convection zone, photosphere, chromosphere, transition zone, corona, and solar wind.	1 – 8
2	Describe the basic properties and composition of each part of the Sun listed above.
3	Explain and describe granulation and supergranulation.
4	Explain what is meant by helioseismology and describe how it has yielded information about the Sun’s structure.	9, 10
5	Define, explain, and state the approximate values of the solar constant and the Sun’s luminosity.	11 – 19
6	Describe mechanisms by which energy is transported from the core of the Sun to its exterior.
7	Explain the process by which the Sun produces energy – fusion and relate this to the law of conservation of mass and energy and the strong nuclear force.
8	Describe and explain the steps of the proton-proton chain in terms of reactions involving fundamental and subatomic particles.
9	Describe efforts to obtain experimental evidence of the fusion process thought to power the Sun including measurements of solar neutrinos.
10	Compare and contrast the concepts quiet Sun and active Sun.	20 – 23
11	Describe the appearance of sunspots and explain their formation in terms of the Sun’s magnetic field.
12	Define and explain the following concepts: sunspot cycle, solar cycle, solar minimum, and solar maximum.
13	Describe and explain active regions of the Sun including prominences, and flares, spicules, and coronal mass ejections.

Reminder: Write out conceptual answers in complete sentences. You must show work to get credit for numerical problems. You may still get credit even if you get the wrong answer so long as you make a reasonable attempt to work the problem.

1. How much more massive is the Sun than the Earth? Let’s make an analogy. Suppose the Earth is like a single person. The Sun is like how many Neyland Stadiums full of people? How could the largest planet, Jupiter, be represented in this analogy? Use the following data to answer the questions: m_sun = 1.99 × 10³⁰ kg, m_earth = 5.97 × 10²⁴ kg, m_jupiter = 1.90 × 10²⁷ kg, Neyland capacity = 100,000 approx.

2. Describe the most distinguishing or defining characteristic for each of the eight major regions of the Sun. In other words what one thing most makes each region unique among the others.

3. State the coolest and hottest parts of the Sun and give the temperatures of these regions. What is the temperature of the “surface” of the Sun – the Sun’s apparent “disk” when we look at it through a filter, or at sunset or sunrise, or by projecting its image?

4. Use Wien’s Law to determine the peak wavelength of radiation for each of the following parts of the Sun: (a) the core at 10,000,000 K, (b) the convection zone at 100,000 K, (c) just below the photosphere at 10,000 K, and (d) the corona at 1,000,000 K. What type of radiation is each?

5. Granules and supergranules are evidence of what process occurring inside the Sun? And how does the process account for the appearance of the granules and supergranules?

6. The Sun is just an assemblage of gas that gets thinner and thinner going outward from the center. Why then does it appear to have a sharp edge or surface when we look at it? (Shouldn’t it look like a fuzzy blob with no clear boundary?)

7. Give the history of “coronium”, and tell how it increased our understanding of the Sun.

8. What is the solar wind?

9. What is helioseismology, and what does it tell us about the Sun? How is it similar and how is it different than seismology as it is applied to Earth?

10. The largest amplitude solar sound waves have periods of about 5 minutes. This is the time taken for the waves to cross from one side of the Sun to the other and back. Calculate the average speed of the wave. How many times faster is this than the speed of regular sound waves traveling through air (v = 343 m/s)? Diameter of Sun = 1.39 × 10⁹ m.

11. Essentially all of the energy existent on Earth originated in the Sun. Describe how energy generated in the core of the Sun eventually reaches the Earth. The energy generated in the core undergoes a series of transformations (changes from one form to another). You should describe each of these transformations and where and how it occurs.

12. How is the equation E = mc² related to the Sun’s enormous energy output? And how does it help to explain that the Sun can continue to produce such energy for billions of years?

13. The Sun’s luminosity is 3.85 × 10²⁶ watts (joules per second). Use E = mc² to determine the amount of mass that must be destroyed and converted into energy every second in order to account for the Sun’s luminosity.

14. The solar wind carries mass away from the Sun at a rate of about 900,000 kg/s. Compare this rate with the rate found in the previous problem. Both factors cause the mass of the Sun to decrease over time. Which is the greater rate and by what multiple?

15. Assume the rates found in the previous problems remain constant. (a) Calculate the number of years for the Sun to vanish and radiate into space – i.e. the time for all of the Sun’s matter to be either converted to energy or carried away by the solar wind. (b) Why is this probably not such a good assumption? In other words, why might we expect the rates to change?

16. What are the beginning ingredients and the end products of the proton-proton chain?

17. Assuming a constant luminosity, calculate the number of years it would take for all of the Sun’s hydrogen (71% of its mass 1.99 × 10³⁰ kg) to be converted into helium. The Sun converts hydrogen into helium at a rate of 6.0 × 10¹¹ kg per seond!

18. (a) What subatomic particles coming from the Sun, that are detected on Earth, are evidence of solar nuclear reactions? (b) How does counting these particles help scientists trying to understand the Sun’s production of energy?

19. The entire reaction sequence of the proton-proton chain generates 4.3 × 10⁻¹² Joules of energy and releases two neutrinos. Based on the Sun’s luminosity (3.85 × 10²⁶ W) how many neutrinos does the Sun produce every second?

20. Sunspots, flares, prominences, spicules, and coronal mass ejections are all aspects of the “active Sun”. What is the underlying cause of all these irregular and sporadic phenomena?

21. Sunspots usually occur in pairs. Why pairs?

22. Every 11 years or so the number of sunspots peaks at a maximum value. However, the sunspots of one maximum are different from those of the next maximum. How so? These observations led astronomers to define what two cycles?

23. The Sun’s differential rotation is responsible for wrapping the solar magnetic field around the Sun (see Fig. 16.19). (a) The rotational period of the Sun's equator, t = 25.1 days, is less than that of its poles, t = 36 days. Calculate how long it takes for material at the solar equator to “lap” the material near the poles – that is, to complete one extra trip around the Sun’s rotation axis. (b) Using the result to part (a), determine how many “laps” will occur from one magnetic reversal to the next.

Objectives/HW

Selected Answers