Chap 11 Practice Questions
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Review Questions
1.
Briefly describe how
gravitational contraction
generates energy. When was it important in the Sun’s history? Explain.
2.
What two forces are balanced in
gravitational equilibrium
? What does it mean for the Sun to be in
energy balance
?
3.
State the Sun’s luminosity, mass, radius, and average surface temperature, and put the numbers in perspective.
4.
Briefly describe the distinguishing features of each of the layers of the Sun shown in
Figure
11.4
.
5.
Distinguish between nuclear
fission
and
fusion.
Which one is used in nuclear power plants? Which one is used by the Sun?
6.
Why does nuclear fusion require high temperatures and pressures?
Electromagnetic repulsion causes nuclei to deflect one another so they never collide.
7.
What is the overall nuclear fusion reaction in the Sun? Briefly describe the proton–proton chain.
8.
Describe how a natural “solar thermostat” keeps the core fusion rate
steady in the Sun.
9.
Describe how energy generated by fusion makes its way to the Sun’s
surface. How long does it take?
10.
How do mathematical models help us learn about conditions inside the Sun, and what gives us confidence in the models?
11.
What are
neutrinos
? What was the
solar neutrino problem,
and how was it solved?
12.
What is
solar activity
? Describe key features including
sunspots, solar prominences, solar flares,
and
coronal mass ejections
.
13.
How do magnetic fields keep sunspots cooler than the surrounding plasma? Explain.
14.
Why are the chromosphere and corona best viewed with ultraviolet and X-ray telescopes, respectively? Briefly explain how we
think the chromosphere and corona are heated.
15.
What is the
sunspot cycle
? Describe the leading model for explaining it. Does the sunspot cycle influence Earth’s climate?
Test Your Understanding
16.
Before Einstein, gravitational contraction appeared to be a perfectly plausible mechanism for solar energy generation.
17.
The solar wind usually flows outward from the Sun, but sometimes it turns around and flows backward.
18.
If fusion in the solar core ceased today, worldwide panic would break out tomorrow as the Sun began to grow dimmer.
19.
Astronomers have recently photographed magnetic fields churning deep beneath the solar photosphere.
20.
I wear a lead vest to protect myself from solar neutrinos.
21.
There haven’t been many sunspots this year, but there ought to be many more in about 5 years.
22.
News of a solar flare caused concern among businesses involved in communication and electrical power generation.
23.
By observing solar neutrinos, we can learn about nuclear fusion deep in the Sun’s core.
24.
If the Sun’s magnetic field somehow disappeared, there would be
no more sunspots on the Sun.
25.
Scientists are currently building an infrared telescope designed to observe fusion reactions in the Sun’s core.
Quick Quiz
26.
Which of these groups of particles has the greatest mass?
a.
a helium nucleus with two protons and two neutrons
b.
four electrons
c.
four individual protons
27.
Which of these layers of the Sun is coolest?
a. core
b.
radiation zone
c. photosphere
28.
X-ray images of the Sun generally show the
a. photosphere.
b. chromosphere.
c. corona.
29.
Scientists estimate the central temperature of the Sun using
a.
probes that measure changes in Earth’s atmosphere.
b.
mathematical models of the Sun.
c.
laboratories that create miniature versions of the Sun.
30.
Sunspots appear darker than their surroundings because they
a.
are cooler than their surroundings.
b.
block some of the sunlight from the photosphere.
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c.
do not emit any light.
31.
At the center of the Sun, fusion converts hydrogen into
a. plasma.
b.
radiation and elements like carbon and nitrogen.
c.
helium, energy, and neutrinos.
32.
Solar energy leaves the core of the Sun in the form of
a. photons.
b.
rising hot gas.
c.
sound waves.
33.
The fact that we observe neutrinos from the Sun provides direct evidence of
a.
fusion in the Sun’s core.
b.
convection in the Sun’s interior.
c.
the existence of the solar wind.
34.
What causes the cycle of solar activity?
a.
changes in the Sun’s fusion rate
b.
changes in the organization of the Sun’s magnetic field
c.
changes in the speed of the solar wind
35.
Which of these things poses the greatest hazard to communication satellites?
a.
photons from the Sun
b.
solar magnetic fields
c.
particles from the Sun
36.
Inside the Sun.
Scientists claim to know what is going on inside the Sun, even though we cannot directly observe the Sun’s interior. What is the basis for these claims, and how are they aligned with the
hallmarks of science outlined in
Section
3.4
?
37.
The Solar Neutrino Problem.
Early solar neutrino experiments detected only about a third of the number of neutrinos predicted by the theory of fusion in the Sun. Why didn’t scientists simply abandon their model at this point? What features of the Sun did the model get
right? What alternatives were there for explaining the mismatch between the predictions and the observations?
38.
The End of Fusion I.
Describe what would happen in the Sun if fusion reactions abruptly ceased.
39.
The End of Fusion II.
If fusion reactions in the Sun were to suddenly cease, would we be able to tell? If so, how?
40.
A Really Strong Force.
How would the interior temperature of the Sun be different if the strong force that binds nuclei together were 10 times as strong?
41.
Covered with Sunspots.
Describe what the Sun would look like from Earth if the entire photosphere were the same temperature as a sunspot.
42.
Inside the Sun.
Describe how scientists determine what the interior of the Sun is like. Could we send a probe into the Sun to measure what is happening there?
43.
Solar Energy Output.
Observations over the past century show that the Sun’s visible-light output varies by less than 1%, but its X-ray output can vary by a factor of 10 or more. Explain why the changes in X-ray output can be so much more pronounced than the changes in visible-light output.