MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) Which two energy sources can help a star maintain its internal thermal pressure?
A) nuclear fusion and gravitational contraction
B) nuclear fission and gravitational contraction
C) nuclear fusion and nuclear fission
D) chemical reactions and gravitational contraction
E) nuclear fusion and chemical reactions
2) What happens when a star exhausts its core hydrogen supply?
A) Its core contracts, but its outer layers expand and the star becomes bigger and brighter.
B) It contracts, becoming smaller and dimmer.
C) It contracts, becoming hotter and brighter.
D) It expands, becoming bigger but dimmer.
E) Its core contracts, but its outer layers expand and the star becomes bigger but cooler and therefore remains at the same brightness.
3) What is a planetary nebula?
A) a disk of gas surrounding a protostar that may form into planets
B) what is left of the planets around a star after a low-mass star has ended its life
C) the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star
D) the molecular cloud from which protostars form
E) the expanding shell of gas that is left when a white dwarf explodes as a supernova
4) On a Hertzsprung\'2DRussell diagram, where on the main sequence would we find stars that have the greatest mass?
A) upper right B) lower right C) upper left D) lower left
5) Which element has the lowest mass per nuclear particle and therefore cannot release energy by either fusion or fission?
A) hydrogen B) oxygen C) silicon D) iron E) uranium
6) On a Hertzsprung\'2DRussell diagram, where would we find stars that are cool and dim?
A) upper right B) lower right C) upper left D) lower left
7) What type of star is our Sun?
A) low-mass star
B) intermediate-mass star
C) high-mass star
8) Which of the following best describes the axes of a Hertzsprung\'2DRussell (H\'2DR) diagram?
A) surface temperature on the horizontal axis and luminosity on the vertical axis
B) mass on the horizontal axis and luminosity on the vertical axis
C) surface temperature on the horizontal axis and radius on the vertical axis
D) mass on the horizontal axis and stellar age on the vertical axis
E) interior temperature on the horizontal axis and mass on the vertical axis
9) Why are neutrinos so difficult to detect?
A) because there are so rare
B) because they have no mass
C) because they move at, or close to, the speed of light
D) because they rarely interact with matter
E) We don't know: this is the essence of the solar neutrino problem.
10) A star of spectral type G lives approximately how long on the main sequence?
A) 1,000 years
B) 10,000 years
C) 1 million years
D) 100 million years
E) 10 billion years
11) From the center outward, which of the following lists the "layers" of the Sun in the correct order?
A) core, radiation zone, convection zone, corona, chromosphere, photosphere
B) core, corona, radiation zone, convection zone, photosphere, chromosphere
C) core, radiation zone, convection zone, photosphere, chromosphere, corona
D) core, convection zone, radiation zone, corona, chromosphere, photosphere
E) core, convection zone, radiation zone, photosphere, chromosphere, corona
12) How do human-built nuclear power plants on Earth generate energy?
A) chemical reactions
B) nuclear fusion
C) nuclear fission
D) converting kinetic energy into electricity
E) converting gravitational potential energy into electricity
13) The core of the Sun is
A) at the same temperature and density as the surface.
B) at the same temperature but denser than the surface.
C) hotter and denser than the surface.
D) constantly rising to the surface through convection.
E) composed of iron.
14) What do we mean when we say that the Sun is in gravitational equilibrium?
A) The hydrogen gas in the Sun is balanced so that it never rises upward or falls downward.
B) The Sun maintains a steady temperature.
C) This is another way of stating that the Sun generates energy by nuclear fusion.
D) There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
E) The Sun always has the same amount of mass, creating the same gravitational force.
15) Cluster ages can be determined from
A) main sequence fitting.
B) main sequence turnoff.
C) pulsating variable stars.
D) spectroscopic binaries.
E) visual binaries.
16) Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?
A) location where they are formed
B) time they are formed
C) luminosity they are formed with
D) mass they are formed with
E) color they are formed with
17) Compared to the star it evolved from, a red giant is
A) hotter and brighter.
B) hotter and dimmer.
C) cooler and brighter.
D) cooler and dimmer.
E) the same temperature and brightness.
18) Studies of sunquakes, or helioseismology, have revealed that
A) the Sun vibrates only on the surface.
B) "sunquakes" are caused by similar processes that create earthquakes on the Earth.
C) the Sun generates energy by nuclear fusion.
D) our mathematical models of the solar interior are fairly accurate.
E) neutrinos from the solar core reach the solar surface easily.
19) On a Hertzsprung\'2DRussell diagram, where would we find stars that are cool and luminous?
A) upper right B) lower right C) upper left D) lower left
20) A star's luminosity is the
A) apparent brightness of the star in our sky.
B) surface temperature of the star.
C) lifetime of the star.
D) total amount of light that the star will radiate over its entire lifetime.
E) total amount of light that the star radiates each second.
21) What are the appropriate units for the Sun's luminosity?
A) watts B) joules C) meters D) Newtons E) kilograms
22) On a Hertzsprung\'2DRussell diagram, where would we find white dwarfs?
A) upper right B) lower right C) upper left D) lower left
23) The helium fusion process results in the production of
A) hydrogen. B) oxygen. C) carbon. D) nitrogen. E) iron.
24) Which is closest to the temperature of the core of the Sun?
A) 10,000 K
B) 100,000 K
C) 1 million K
D) 10 million K
E) 100 million K
25) The spectral sequence in order of decreasing temperature is
A) OFBAGKM.
B) OBAGFKM.
C) OBAFGKM.
D) ABFGKMO.
E) BAGFKMO.
26) Compared to the star it evolved from, a white dwarf is
A) hotter and brighter.
B) hotter and dimmer.
C) cooler and brighter.
D) cooler and dimmer.
E) the same temperature and brightness.
27) Why does a star grow larger after it exhausts its core hydrogen?
A) The outer layers of the star are no longer gravitationally attracted to the core.
B) Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward.
C) Helium fusion in the core generates enough thermal pressure to push the upper layers outward.
D) Helium fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward.
E) The internal radiation generated by the hydrogen fusion in the core has heated the outer layers enough that they can expand after the star is no longer fusing hydrogen.
28) What processes are involved in the sunspot cycle?
A) gravitational contraction of the Sun
B) wave motions in the solar interior
C) variations of the solar thermostat
D) the winding of magnetic field lines due to differential rotation
29) What happens to the core of a star after a planetary nebula occurs?
A) It contracts from a protostar to a main-sequence star.
B) It breaks apart in a violent explosion.
C) It becomes a white dwarf.
D) It becomes a neutron star.
E) none of the above
30) What is the average temperature of the surface of the Sun?
A) 1 million K B) 100,000 K C) 10,000 K D) 6,000 K E) 1,000 K
31) Which layer of the Sun do we normally see?
A) photosphere
B) corona
C) chromosphere
D) convection zone
E) radiation zone
32) The phase of matter in the Sun is
A) gas.
B) plasma.
C) liquid.
D) solid.
E) a mixture of all of the above.
33) Suppose you put two protons near each other. Because of the electromagnetic force, the two protons will
A) collide.
B) remain stationary.
C) attract each other.
D) repel each other.
E) join together to form a nucleus.
34) What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure?
A) The core contracts and becomes a white dwarf.
B) The core contracts and becomes a ball of neutrons.
C) The core contracts and becomes a black hole.
D) The star explodes violently, leaving nothing behind.
E) Gravity is not able to overcome neutron degeneracy pressure.
35) How does the Sun generate energy today?
A) nuclear fission
B) nuclear fusion
C) chemical reactions
D) gravitational contraction
E) gradually expanding in size
36) If the distance between us and a star is doubled, with everything else remaining the same, the luminosity
A) is decreased by a factor of four, and the apparent brightness is decreased by a factor of four.
B) is decreased by a factor of two, and the apparent brightness is decreased by a factor of two.
C) remains the same, but the apparent brightness is decreased by a factor of two.
D) the luminosity remains the same, but the apparent brightness is decreased by a factor of four.
E) is decreased by a factor of four, but the apparent brightness remains the same.
37) Sunspots are cooler than the surrounding solar surface because
A) they are regions where convection carries cooler material downward.
B) strong magnetic fields slow convection and prevent hot plasma from entering the region.
C) magnetic fields trap ionized gases that absorb light.
D) there is less fusion occurring there.
E) magnetic fields lift material from the surface of the Sun, cooling off the material faster.
38) After a supernova event, what is left behind?
A) always a white dwarf
B) always a neutron star
C) always a black hole
D) either a white dwarf or a neutron star
E) either a neutron star or a black hole
39) Which of the following sequences correctly describes the stages of life for
a low-mass star?
A) red giant, protostar, main-sequence, white dwarf
B) white dwarf, main-sequence, red giant, protostar
C) protostar, red giant, main-sequence, white dwarf
D) protostar, main-sequence, white dwarf, red giant
E) protostar, main-sequence, red giant, white dwarf
40) Which event marks the beginning of a supernova?
A) the onset of helium burning after a helium flash in a star with mass comparable to that of the Sun
B) the sudden outpouring of X rays from a newly formed accretion disk
C) the sudden collapse of an iron core into a compact ball of neutrons
D) the beginning of neon burning in an extremely massive star
E) the expansion of a low-mass star into a red giant
The following questions refer to the sketch below of an H-R diagram for a star cluster.
Figure 14.2
41) Consider the star to which the arrow points. Which of the following statements about this star is not true?
A) It is significantly less massive than the Sun.
B) It is larger in radius than the Sun.
C) It is brighter than the Sun.
D) Its surface temperature is lower than the Sun's.
E) Its core temperature is higher than the Sun's.
1) Answer: A
2) Answer: A
3) Answer: C
4) Answer: C
5) Answer: D
6) Answer: B
7) Answer: A
8) Answer: A
9) Answer: D
10) Answer: E
11) Answer: C
12) Answer: C
13) Answer: C
14) Answer: D
15) Answer: B
16) Answer: D
17) Answer: C
18) Answer: D
19) Answer: A
20) Answer: E
21) Answer: A
22) Answer: D
23) Answer: C
24) Answer: D
25) Answer: C
26) Answer: B
27) Answer: B
28) Answer: D
29) Answer: C
30) Answer: D
31) Answer: A
32) Answer: B
33) Answer: D
34) Answer: C
35) Answer: B
36) Answer: D
37) Answer: B
38) Answer: E
39) Answer: E
40) Answer: C
41) Answer: A
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