UCLA Astro 3 Final UPDATED ACTUAL
Exam Questions and CORRECT Answers
How does a 1.2-solar-mass white dwarf compare to a 0.9-solar-mass white dwarf?
Select one:
a. It has a larger radius.
b. It has a higher surface temperature.
c. It has a smaller radius.
d. It has a lower surface temperature.
e. It is supported by neutron, rather than electron, degeneracy pressure. - CORRECT
ANSWER - c. It has a smaller radius.
Compared to the star it evolved from, a white dwarf is
Select one:
a. hotter and brigher
b. hotter and dimmer
c. cooler and brighter
d. cooler and dimmer
e. the same temperature - CORRECT ANSWER - b. hotter and dimmer
Nuclear fusion proceeds in stars towards heavier and heavier elements. At what element does
this nucleosynthetic chain stop?
Select one:
a. Hydrogen
b. Helium
c. Carbon
d. Silicon
,e. Iron - CORRECT ANSWER - e. Iron
What is the ultimate fate of an isolated white dwarf?
Select one:
a. It will cool down and become a cold black dwarf.
b. As gravity overwhelms the electron degeneracy pressure, it will explode as a nova.
c. As gravity overwhelms the electron degeneracy pressure, it will explode as a supernova.
d. As gravity overwhelms the electron degeneracy pressure, it will become a neutron star.
e. The electron degeneracy pressure will eventually overwhelm gravity and the white dwarf will
slowly evaporate. - CORRECT ANSWER - a. It will cool down and become a cold black
dwarf.
After a massive-star supernova, what is left behind?
Select one:
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 - CORRECT ANSWER - e. either a neutron star or
a black hole
The thermal pressure of a gas depends on
Select one:
a. density only.
b. temperature only.
c. density and temperature.
,d. composition.
e. gravity. - CORRECT ANSWER - c. density and temperature.
Which of the following statements is not true about stars with main sequence masses greater than
8 solar masses?
Select one:
a. The dominant nuclear fusion process in their cores when they're on the main sequence is the
CNO cycle.
b. Some of them end up as white dwarfs.
c. Before the supernova explosion, their cores are composed of iron.
d. They follow roughly horizontal tracks in the Hertzsprung-Russell diagram.
e. Their core temperatures are hotter than the core temperature of the Sun. - CORRECT
ANSWER - b. Some of them end up as white dwarfs.
What is the Schwarzschild radius for a 10 solar mass black hole?
Select one:
a. 3 km
b. 30 km
c. Impossible to determine.
d. 10 km
e. 1.4 km - CORRECT ANSWER - b. 30 km
What is the upper limit to the mass of a neutron star?
Select one:
a. There is an upper limit of approximately 3 solar masses, but we do not yet know precisely
what it is.
, b. precisely 2 solar masses
c. 1.4 solar masses
d. There is no upper limit.
e. 1 solar mass - CORRECT ANSWER - a. There is an upper limit of approximately 3
solar masses, but we do not yet know precisely what it is.
Which of the following statements about stages of nuclear burning (i.e., first-stage hydrogen
burning, second-stage helium burning, etc.) in a massive star is not true?
Select one:
a. Each successive stage of fusion requires higher temperatures than the previous stages.
b. As each stage ends, the core shrinks further.
c. Each successive stage lasts for approximately the same amount of time.
d. The final stage before core collapse is fusion into iron.
e. The CNO cycle dominates hydrogen fusion in the core on the main sequence. - CORRECT
ANSWER - c. Each successive stage lasts for approximately the same amount of time
Which of the following types of galaxies are most commonly found in large clusters?
Select one:
a. spirals
b. ellipticals
c. lenticulars
d. irregulars - CORRECT ANSWER - b. ellipticals
The disk component of a spiral galaxy includes which of the following components?
Select one:
a. halo
Exam Questions and CORRECT Answers
How does a 1.2-solar-mass white dwarf compare to a 0.9-solar-mass white dwarf?
Select one:
a. It has a larger radius.
b. It has a higher surface temperature.
c. It has a smaller radius.
d. It has a lower surface temperature.
e. It is supported by neutron, rather than electron, degeneracy pressure. - CORRECT
ANSWER - c. It has a smaller radius.
Compared to the star it evolved from, a white dwarf is
Select one:
a. hotter and brigher
b. hotter and dimmer
c. cooler and brighter
d. cooler and dimmer
e. the same temperature - CORRECT ANSWER - b. hotter and dimmer
Nuclear fusion proceeds in stars towards heavier and heavier elements. At what element does
this nucleosynthetic chain stop?
Select one:
a. Hydrogen
b. Helium
c. Carbon
d. Silicon
,e. Iron - CORRECT ANSWER - e. Iron
What is the ultimate fate of an isolated white dwarf?
Select one:
a. It will cool down and become a cold black dwarf.
b. As gravity overwhelms the electron degeneracy pressure, it will explode as a nova.
c. As gravity overwhelms the electron degeneracy pressure, it will explode as a supernova.
d. As gravity overwhelms the electron degeneracy pressure, it will become a neutron star.
e. The electron degeneracy pressure will eventually overwhelm gravity and the white dwarf will
slowly evaporate. - CORRECT ANSWER - a. It will cool down and become a cold black
dwarf.
After a massive-star supernova, what is left behind?
Select one:
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 - CORRECT ANSWER - e. either a neutron star or
a black hole
The thermal pressure of a gas depends on
Select one:
a. density only.
b. temperature only.
c. density and temperature.
,d. composition.
e. gravity. - CORRECT ANSWER - c. density and temperature.
Which of the following statements is not true about stars with main sequence masses greater than
8 solar masses?
Select one:
a. The dominant nuclear fusion process in their cores when they're on the main sequence is the
CNO cycle.
b. Some of them end up as white dwarfs.
c. Before the supernova explosion, their cores are composed of iron.
d. They follow roughly horizontal tracks in the Hertzsprung-Russell diagram.
e. Their core temperatures are hotter than the core temperature of the Sun. - CORRECT
ANSWER - b. Some of them end up as white dwarfs.
What is the Schwarzschild radius for a 10 solar mass black hole?
Select one:
a. 3 km
b. 30 km
c. Impossible to determine.
d. 10 km
e. 1.4 km - CORRECT ANSWER - b. 30 km
What is the upper limit to the mass of a neutron star?
Select one:
a. There is an upper limit of approximately 3 solar masses, but we do not yet know precisely
what it is.
, b. precisely 2 solar masses
c. 1.4 solar masses
d. There is no upper limit.
e. 1 solar mass - CORRECT ANSWER - a. There is an upper limit of approximately 3
solar masses, but we do not yet know precisely what it is.
Which of the following statements about stages of nuclear burning (i.e., first-stage hydrogen
burning, second-stage helium burning, etc.) in a massive star is not true?
Select one:
a. Each successive stage of fusion requires higher temperatures than the previous stages.
b. As each stage ends, the core shrinks further.
c. Each successive stage lasts for approximately the same amount of time.
d. The final stage before core collapse is fusion into iron.
e. The CNO cycle dominates hydrogen fusion in the core on the main sequence. - CORRECT
ANSWER - c. Each successive stage lasts for approximately the same amount of time
Which of the following types of galaxies are most commonly found in large clusters?
Select one:
a. spirals
b. ellipticals
c. lenticulars
d. irregulars - CORRECT ANSWER - b. ellipticals
The disk component of a spiral galaxy includes which of the following components?
Select one:
a. halo
