Stellar Evolution
1.
What is the source of energy in a protostar?
a. Hydrogen
fusion to helium.
b. Uranium
fission to lighter elements.
c. Gravitational
contraction.
d. A
variety of chemical reactions.
e. None
of these.
2.
Interstellar gas clouds
may collapse to form stars if they
a. have very high temperatures.
b. encounter a shock wave.
c. rotate rapidly.
d. are located near main sequence
spectral type K and M stars.
e. all of the above.
3.
Which of the following is the first to develop?
a. OB
associations
b. T
Tauri stars
c. interstellar
gas and dust clouds
d. pulsars
e. red
giants
4.
Explain why nuclear fusion takes place only in the centers
of main sequence stars rather than on their surfaces as well.
a. Pressures
are only high enough in the center.
b. Densities
are only high enough in the center.
c. Opacities
are only high enough in the center.
d. The
nuclear fuel is only in the center.
e. None
of these.
5.
Why do stars that are more massive have shorter
main-sequence lifetimes?
a. They
are hotter than less massive stars.
b. They
fuse hydrogen to helium at much greater rates than do less massive stars.
c. They
have less nuclear fuel than less massive stars.
d. They
are denser than less massive stars.
e. None
of these.
6.
In what form is energy carried away in the proton-proton
chain?
a. By
positrons.
b. By
neutrinos.
c. By
gamma rays.
d. All
of these.
e. None
of these.
7.
The
carbon-nitrogen-oxygen (CNO) cycle
a. operates at a slightly lower
temperature than the proton-proton chain.
b. is most efficient in star less
massive than the sun.
c. occurs when carbon and oxygen
combine to form nitrogen, which produces energy.
d. produces the energy responsible for
bipolar flows.
e. combines four hydrogen nuclei to
form one helium nucleus, which produces energy.
8.
Which one of the following is not a class of star cluster?
a. galactic
clusters
b. open
clusters
c. closed
clusters
d. globular
clusters
e. stellar
associations.
9.
Star clusters are
important to our study of stars because
a. all stars formed in star clusters.
b. the sun was once a member of a
globular cluster.
c. they give us a method to test the
our theories and models of stellar evolution.
d. they are the only objects that
contain Cepheid variables.
e. all of the above
10.
Which of the following is not an assumption made in the
study of star clusters:
a. all
the stars are at the same distance
b. all
the stars formed at the same time
c. all
the stars have the same chemical composition
d. all
the stars have the same mass
e. all
the above are assumed to be true.
11.
For stars in a cluster, observed differences in apparent
magnitude from one star to another are due to differences in
a. absolute
magnitude
b. chemical
composition
c. distance
d. age
12.
Main sequence fitting is used primarily to determine a
cluster's
a. mass
b. age
c. apparent
magnitude
d. distance
e. main
sequence.
13.
Stars on the upper end of the main sequence next evolve into
a. red
dwarfs
b. lower
main sequence stars
c. solar-type
stars
d. white
dwarfs
e. red
giants.
14.
The main sequence turn-off is useful in determining a
cluster's
a. mass
b. age
c. distance
d. apparent
magnitude
e. velocity.
15.
A T Tauri star is one which is
a. like
the Sun
b. variable
and shedding mass
c. old
and shedding mass
d. becoming
a white dwarf
e. a
main sequence star.
16.
Protostars in dark, dusty regions may be studied in the
______ spectral region.
a. x-ray
b. ultraviolet
c. visual
d. infrared
e. gamma-ray
17.
During the formation of a star, the contraction stops when
a. the
star collapses into a black hole
b. the
star collapses into a white dwarf
c. hydrogen
burning becomes the dominant energy source
d. helium
burning becomes the dominant energy source
e. the
star becomes a T Tauri star.
18.
A cluster with a main sequence turn-off at spectral type A2
is ______ a cluster with its turn-off at F2.
a. younger
than
b. older
than
c. the
same age as
d. more
distant than
e. less
distant than.
19.
In which section of the H-R diagram will most stars spend
the greatest part of their lifetimes?
a. supergiant
b. white
dwarf
c. subgiant
d. red
giant
e. main
sequence
20.
As a star converts its hydrogen to helium, the position of
the star in the H-R diagram moves mostly toward
a. higher
density
b. lower
temperature
c. higher
luminosity
d. lower
luminosity
e. lower
radius.
21.
When the core hydrogen has been converted to helium, the
core will next
a. collapse
b. expand
c. burn
helium
d. decrease
in temperature
e. explode.
22.
When hydrogen burning in the core stops, the core contracts
and heats up again. Why doesn't
hydrogen-burning start again?
a. Because
helium starts to burn.
b. Because
there is no more hydrogen in the core.
c. Because
the star becomes a red giant.
d. Because
the star becomes a white dwarf.
e. None
of these.
23.
The lowest-mass stars
cannot become giants because
a. they do not contain helium.
b. they rotate too slowly.
c. they cannot heat their centers hot
enough.
d. they contain strong magnetic fields.
e. they never use up their hydrogen.
24.
Which of the following occurs during and after the phase of
the hydrogen burning shell?
a. the
core shrinks until the star becomes a white dwarf
b. the
helium flash occurs
c. the
core temperature decreases while the envelope temperature increases
d. the
star becomes a supernova
e. the
envelope expands and cools, and the star becomes a red giant.
25.
As a perfect gas is heated, it will
a. expand
b. contract
c. neither
expand nor contract
d. oscillate.
26.
For a star with the Sun's mass, you expect that after all
the hydrogen in the core is used up, the star will next become
a. a
nova
b. a
supernova
c. a
supergiant
d. a
red giant
e. a
white dwarf
27.
Giant and supergiant
stars are rare because
a. they do not form as often as main
sequence stars.
b. the giant and supergiant stage is
unstable.
c. the giant and supergiant stage is
very short.
d. helium is very rare.
e. helium flash destroys many of the
stars before they can become giants and supergiants.
28.
A star will experience
a helium flash if
a. it is more massive than about 6
solar masses.
b. its core contains oxygen and helium.
c. its mass on the main sequence was
less than 0.1 solar masses.
d. it is a supergiant.
e. its core is degenerate when helium
ignites.
29.
At some time in its lifetime, the Sun will become a
a. white
dwarf
b. blue
supergiant
c. neutron
star
d. black
hole
e. B-type
main sequence star.
30.
Stars more massive than the Sun obtain their energy while on
the main sequence from
a. the
proton-proton cycle
b. the
CNO cycle
c. the
triple-alpha reaction
d. gravitational
contraction.
31.
A catastrophic loss of mass occurs in a
a. helium
flash
b. neutron
star
c. supernova
d. planetary
nebula ejection
e. T
Tauri star.
32.
Heavy elements which are mixed into the material from which
new generations of stars may be formed come from
a. the
big bang
b. planetary
nebulae
c. supernovae
d. super-neutron
stars
e. Wolf-Rayet
stars.
33.
The most massive stars are thought to end up as
a. white
dwarfs
b. planetary
nebulae
c. neutron
stars
d. black
holes.
34.
An important difference between the evolution of a massive
star and a 1-solar-mass star is
a. the
massive star does not have a long main-sequence phase *
b. the
massive star does not have periods when it has hydrogen-burning or
helium-burning shells
c. the
massive star does not have a red giant phase
d. the
massive star does not go through a wide range of temperatures over its
evolution
35.
How does comparing the H-R diagrams of galactic and globular
clusters confirm astronomers' general ideas about stellar evolution?
a. The
diagrams for different clusters are all the same.
b. The
diagrams indicate that all stars have the same age.
c. The
diagrams show that the top end of the main sequence turns off at different
points, indicating that stars that are more massive evolve faster.
36.
The heaviest element that can be created in normal stellar
nucleosynthesis is
a. iron
b. carbon
c. helium
d. silicon
e. uranium
37.
Basically, stars evolve because they
a. are
made of hydrogen
b. are
gases
c. give
off energy
d. are
larger than planets
e. none
of the above
38.
One major difference between the stars in an open (galactic)
cluster and those in a globular one is that the stars in globular are
a. more
massive
b. younger
c. deficient
in heavy elements (metals)
d. never
to evolve anymore