Chapter 12
Our Sun: Local Star
1. In order to find the earth-sun distance in units such as kilometers, we:
A. bounce radar signals off the sun.
B. bounce radar signals off the moon.
C. bounce radar signals off Venus.
D. know the light travel time from the sun to the earth.
2. In order to find the sun's mass in kilograms, we need everything BUT:
A. Newton's law of gravitation.
B. Newton's second law.
C. the earth's mass.
D. the earth-sun distance in units such as kilometers.
3. In order to determine the sun's luminosity, you MUST know the:
A. size of the earth.
B. size of the sun.
C. mass of the sun.
D. earth-sun distance in units such as kilometers.
4. Consider the sun's continuous emission as that of a blackbody radiator. Then one way to infer the
sun's surface temperature is to measure the:
A. longest wavelength the sun emits.
B. shortest wavelength the sun emits.
C. peak wavelength the sun emits.
D. continuous spectrum after it passes through the air.
5. In which region of the sun do photons find that the opacity suddenly becomes very low so that
they are free to fly off into space?
A. core.
B. photosphere.
C. chromosphere.
D. corona.
6. Using a visible-light spectroscope, we see directly which elements exist in the sun's:
A. core.
B. photosphere.
C. chromosphere.
D. corona.
7. The two most abundant solar elements, in terms of its mass, are:
A. carbon and oxygen
B. helium and carbon.
C. hydrogen and oxygen.
D. hydrogen and helium.
8. What is inferred to be the source of the sun's energy now?
A. Fusion reactions in the core.
B. Gravitational energy released by collapse.
C. Fission reactions in the core.
D. Oxidation of materials such as carbon.
9. As the sun ages, the chemical composition of its core changes so that it contains a lower
percentage of ________ and a greater percentage of ________.
A. helium, hydrogen
B. uranium, lead
C. hydrogen, helium
D. oxygen, carbon
10. For what reason do astronomers want to observe and measure neutrinos from the sun?
A. Neutrinos are more energetic than photons from the sun.
B. Neutrinos are easier to detect than photons.
C. Neutrinos give direct information about the photosphere.
D. Neutrinos give direct information about the sun's core.
11. Which of these regions of the sun has the HIGHEST temperature?
A. Core.
B. Photosphere.
C. Chromosphere.
D. Corona.
12. Two important characteristics of sunspots are:
A. low temperature and intense magnetic fields.
B. high temperature and intense magnetic fields.
C. high temperature and weak magnetic fields.
D. low temperature and no magnetic fields.
13. Consider two regions of the sun where the number density of the gas is the same but the
temperature of one region is twice that of the other. What can you say about the gas particles of the
hotter region?
A. They have much more mass.
B. They move around half as fast on the average.
C. They move around twice as fast on the average.
D. They move around four times as fast on the average.
14. The primary transport system for heat to get from the core of our Sun to the outside, as
evidenced by its "granular appearance" is:
A. radiation.
B. conduction.
C. convection.
D. levitation.
15. The theoretical concept of a "black body" is used to determine the temperature of our sun. A
black body is an object that:
A. emits and absorbs all radiation with 50% efficiency.
B. emits and absorbs all radiation with 100% efficiency..
C. contains no material and is therefore a vacuum.
D. warps spacetime into a singularity.
16. One recent development in astrophysics seems to confuse our understanding of the process of
mass conversion to energy in the core of our Sun. What is it?
A. The Sun's surface temperature is decreasing too rapidly.
B. The gamma-rays from the Sun are the wrong wavelength.
C. The Sun's spectrum should be blue-shifted, but is not.
D. There aren't enough neutrinos emitted from the Sun's core.
17. Solar prominences are clouds of gas above the Sun's photosphere, that are caused:
A. by mass ejection due to rapid rotation of the Sun.
B. by the effects of the magnetic fields near active regions.
C. by mass ejection due to intense convective effects.
D. by the gravitational attraction of the Earth every 22 years.
18. Increased activity of the Sun as evidenced by an increased occurrence of sunspots and
prominences is associated with:
A. solar flares;
B. a reduction in the period of solar activity.
C. no neutrino emission from the Sun.
D. the Vernal equinox.
19. The by-products of fusion reactions in the core of the Sun release:
A. energy in the form of gamma-rays, and neutrinos.
B. helium and hydrogen.
C. metallic hydrogen.
D. cool transparent gases.
20. One way to measure the distance to Stars (near to us) is to use trigonometric parallax. To
improve this technique, you can:
A. make your measurements from Mercury.
B. reflect radar off of the surface of the star and compare the distance.
C. confine your observations to one-fourth of a year
D. make your measurements from an orbit larger than the earth's.
21.-23. Match these temperatures with their significance:
A. 3,000 K .9. 6,000 K C. 1-2 million K D. 8-10 million K
21. Approximate temperature of the Sun's corona.
22. Approximate temperature of the Sun's photosphere.
23. Approximate temperature of the Sun's core.
24. To detennine the mass of our Sun, we:
A. use the trigonometric parallax.
B. extrapolate from the density of the chromosphere.
C. use Kepler's third law and Newton's law of gravity.
D. use the observed temperature and spectral analysis.
25. The energy produced in the fusion reactions within the core of our Sun comes from:
A. the absorption of neutrinos in the photosphere.
B. atomic energy associated with the electron orbitals.
C. interactions of molecules with the magnetic field.
D. mass conversion.
26. The solar activity that varies over a period of 22 years is evident when observing:
A. the spectral emission of Helium in the photosphere.
B. the migration of sunspots toward the solar equator.
C. increased activity of prominences and coronal mass ejections.
D. the variability of similar stars.
27. Why is the sun's chromosphere much hotter that the photosphere?
Probably it is the result of:
A. mass ejection caused by the rapid rotation of the Sun.
B. the effects of the magnetic fields near active regions.
C. mass ejection caused by intense convective effects.
D. the gravitational attraction of the earth every 22 years.
28. The size of the sun is such that ______________ could be placed at the center and _________
would still be confined within its photosphere.
A. the earth/the moon’s orbit
B. Jupiter/the orbit of Io
C. Venus/the orbit of Mercury
D. Venus/the orbit of the earth
29. Wien’s Law notes that the wavelength at which the energy output from a black body peaks is:
A. directly proportional to wavelength.
B. inversely proportional to temperature.
C. inversely proportional to wavelength.
D. directly proportional to temperature.
30. Which of these could best be seen during a total solar eclipse?
A. Sunspots.
B. Prominences.
C. Granulation.
D. The photosphere.
31. Auroral displays on Earth are most closely related to:
A. intense solar flares.
B. huge sunspot groups.
C. a spotless sun.
D. radio outbursts from Jupiter.
32. If the last solar maxima was in 1991, when is the next likely to occur?
A. 1994.
B. 1998.
C. 2002.
D. 2010.
33. The net effect of a large amount of sunspot activity is to:
A. slightly warm the earth.
B. slightly cool the earth.
C. no correlation has been noted.
D. the changes from cycle to cycle.
34. The magnetic polarity of sunspot pairs in each hemisphere:
A. has switched in less than an hour.
B. switches from week to week.
C. switches with each new sunspot cycle.
D. has stayed stable for as long as we have observed it
ESSAYS
1. What is the average length of the sunspot cycle? Name a notable disruption in this cycle, and
describe its climatic effect.
2. The solar corona is much hotter than the photosphere. yet it is the latter that dominates our
daytime sky. When can we see the corona, and why is it so faint?
3. Explain why the photosphere gives off a continuous spectrum with some absorption lines, yet the
spectrum of the corona is bright emission lines.
4. Relate sunspots and prominences to solar magnetism.
S. Relate flares to sunspots and prominences.
6. Describe an observable interaction between the solar wind and our magnetic field. Why is this
interaction most noticeable at the poles?
7. Explain why when a solar flare occurs, the X-rays arrive first, followed hours later by the
electron storm, and finally about three days later by the proton events.