MULTIPLE CHOICE.  Choose the one alternative that best completes the statement or answers the question.

 

1)  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.

 

2)  What are the appropriate units for the Sun's luminosity?

 

A) watts B)  joules C)  meters D)  Newtons E)  kilograms

 

3)  Which layer of the Sun do we normally see?

 

A) photosphere

B) corona

C) chromosphere

D) convection zone

E) radiation zone

 

4)  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.

 

5)  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

 

6)  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.

 

7)  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.

 

8)  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.

 

9)  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

 

10)  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.

 

11)  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.

 

12)  The spectral sequence in order of decreasing temperature is

 

A) OFBAGKM.

B) OBAGFKM.

C) OBAFGKM.

D) ABFGKMO.

E) BAGFKMO.

 

13)  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

 

14)  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

 

15)  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

 

16)  On a Hertzsprung\'2DRussell diagram, where would we find white dwarfs?

 

A) upper right B)  lower right C)  upper left D)  lower left

 

17)  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

 

18)  Cluster ages can be determined from

 

A) main sequence fitting.

B) main sequence turnoff.

C) pulsating variable stars.

D) spectroscopic binaries.

E) visual binaries.

 

19)  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

 

20)  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

 

21)  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.

 

22)  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.

 

23)  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


 

1)  Answer:  D

 

2)  Answer:  A

 

3)  Answer:  A

 

4)  Answer:  B

 

5)  Answer:  C

 

6)  Answer:  D

 

7)  Answer:  D

 

8)  Answer:  D

 

9)  Answer:  D

 

10)  Answer:  E

 

11)  Answer:  D

 

12)  Answer:  C

 

13)  Answer:  A

 

14)  Answer:  A

 

15)  Answer:  C

 

16)  Answer:  D

 

17)  Answer:  E

 

18)  Answer:  B

 

19)  Answer:  A

 

20)  Answer:  C

 

21)  Answer:  B

 

22)  Answer:  C

 

23)  Answer:  C