Review
for Final Exam Fall2003 RBF
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 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
3) 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.
4) 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.
5) 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?
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 creates an element with a higher atomic weight.
D) Each successive
stage lasts for approximately the same amount of time.
6) 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
7) Why is Supernova 1987A particularly important
to astronomers?
A) It occurred
only a few dozen light-years from Earth.
B) It provided the
first evidence that supernovae really occur.
C) It provided the
first evidence that neutron stars really exist.
D) It was the
first supernova detected in nearly 400 years.
E) It was the
nearest supernova detected in nearly 400 years.
8) White dwarfs are so called because
A) the are both
very hot and very small.
B) they are the
end-products of small, low-mass stars.
C) they are the
opposite of black holes.
D) it amplifies
the contrast with red giants.
E) they are
supported by electron degeneracy pressure.
9) Which of the following is closest in mass to a
white dwarf?
A) the Moon B)
the Earth C) Jupiter D) the Sun
10) Suppose a white dwarf is gaining mass because
of accretion in a binary system. What
happens
if the mass someday reaches the 1.4-solar-mass limit?
A) The white dwarf
undergoes a catastrophic collapse, leading to a type of supernova that is
somewhat different from that which occurs in a massive star but is comparable
in energy.
B) The white
dwarf, which is made mostly of carbon, suddenly becomes much hotter in
temperature and therefore is able to begin fusing the carbon. This turns the
white dwarf back into a star supported against gravity by ordinary pressure.
C) The white dwarf
immediately collapses into a black hole, disappearing from view.
D) A white dwarf
can never gain enough mass to reach the limit because a strong stellar wind
prevents the material from reaching it in the first place.
11) What kind of pressure supports a white dwarf?
A) neutron
degeneracy pressure
B) electron
degeneracy pressure
C) thermal
pressure
D) radiation
pressure
E) all of the
above
12) After a massive star supernova, 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
13) From an observational standpoint, what is a pulsar?
A) a star that
slowly changes its brightness, getting dimmer and then brighter with a period
of anywhere from a few hours to a few weeks
B) an object that
emits flashes of light several times per second or more, with near perfect
regularity
C) an object that
emits random "pulses" of light that sometimes occur only a fraction
of a
second apart and other times stop for several
days at a time
D) a star that
changes color rapidly, from blue to red and back again
14) What causes the radio pulses of a pulsar?
A) The star
vibrates.
B) As the star
spins, beams of radio radiation sweep through space. If one of the beams
crosses
the Earth, we observe a pulse.
C) The star
undergoes periodic explosions of nuclear fusion that generate radio emission.
D) The star's
orbiting companion periodically eclipses the radio waves emitted by the main
pulsar.
E) A black hole
near the star absorbs energy and re-emits it as radio waves.
15) How does a black hole form from a massive
star?
A) During a
supernova, if a star is massive enough for its gravity to overcome neutron
degeneracy of the core, the core will be
compressed until it becomes a black hole.
B) Any star that
is more massive than 8 solar masses will undergo a supernova explosion and
leave behind a black-hole remnant.
C) If enough mass
is accreted by a white-dwarf star so that it exceeds the 1.4-solar-mass limit,
it
will undergo a supernova explosion and leave
behind a black-hole remnant.
D) If enough mass
is accreted by a neutron star, it will undergo a supernova explosion and leave
behind a black-hole remnant.
E) A black hole
forms when two massive main-sequence stars collide.
16) What do we mean by the singularity of a
black hole?
A) There are no
binary black holes each one is isolated.
B) An object can
become a black hole only once, and a black hole cannot evolve into anything
else.
C) It is the
center of the black hole, a place of infinite density where the known laws of
physics
cannot describe the conditions.
D) It is the edge
of the black hole, where one could leave the observable universe.
E) It is the
"point of no return" of the black hole; anything closer than this
point will not be
able to
escape the gravitational force of the black hole.
17) If you were to come back to our Solar System
in 6 billion years, what might you expect
to
find?
A) a red giant
star
B) a white dwarf
C) a rapidly
spinning pulsar
D) a black hole
E) Everything will
be pretty much the same as it is now.
18) What kinds of objects lie in the disk of our
galaxy?
A) open clusters
B) O and B stars
C) old K and M
stars
D) gas and dust
E) all of the
above
19) Harlow Shapley concluded that the Sun was not
in the center of the Milky Way Galaxy by
A) looking at the
shape of the "milky band" across the sky.
B) mapping the
distribution of stars in the galaxy.
C) mapping the
distribution of globular clusters in the galaxy.
D) mapping the
distribution of gas clouds in the spiral arms.
E) looking at
other nearby spiral galaxies.
20) All the iron on Earth originated from
A) white dwarfs.
B) nuclear fusion
within the cores of low-mass stars.
C) nuclear fusion
within the cores of high-mass stars.
D) the Big Bang,
when the universe first began.
E) the bombardment
of comets in the late stages of planet formation.
21) What is the most common form of gas in the
interstellar medium?
A) molecular
hydrogen
B) molecular
helium
C) atomic hydrogen
D) atomic helium
E) ionized
hydrogen
22) Compared with our Sun, most stars in the halo
are
A) young, red, and
dim and have fewer heavy elements.
B) young, blue,
and bright and have much more heavy element material.
C) old, red, and
dim and have fewer heavy elements.
D) old, red, and
dim and have much more heavy element material.
E) old, red, and
bright and have fewer heavy elements.
23) Which types of galaxies have a clearly defined
spheroidal component?
A) spirals only
B) ellipticals
only
C) lenticulars
only
D) irregulars only
E) all but
irregulars
24) How does a lenticular galaxy differ
from a normal spiral galaxy?
A) It has no
bulge.
B) It has an
elongated bulge resembling a bar more than a sphere.
C) It is flatter
in shape.
D) It has no gas
or dust.
E) It has no
spiral arms.
25) Why are Cepheid variables important?
A) Cepheid
variables are stars that vary in brightness because they harbor a black hole.
B) Cepheids are
pulsating variable stars, and their pulsation periods are directly related to
their true luminosities. Hence, we can use
Cepheids as "standard candles" for distance
measurements.
C) Cepheids are a
type of young galaxy that helps us understand how galaxies form.
D) Cepheids are
supermassive stars that are on the verge of becoming supernovae and therefore
allow us to choose candidates to watch if we hope to observe a supernova in the
near future.
26) How was Edwin Hubble able to use his discovery
of a Cepheid in Andromeda to prove
that
the "spiral nebulae" were actually entire galaxies?
A) There are no
Cepheids in the Milky Way, so his discovery proved that it had to be in another
galaxy.
B) He measured the
stellar parallax of the Cepheid in Andromeda, was able to determine the
distance to it, and showed that it was far
outside the Milky Way Galaxy.
C) He used
main-sequence fitting to determine the distance to Andromeda and show that it
was far outside the Milky Way Galaxy.
D) From the
period-luminosity relation for Cepheids, he was able to determine the distance
to
Andromeda and show that it was far outside the
Milky Way Galaxy.
E) Since a Cepheid
is a type of luminous galaxy, when he found it in Andromeda he was able to
prove that Andromeda was a separate galaxy
from the Milky Way.
27) What is Hubble's law?
A) The longer the
time period between peaks in brightness, the greater the luminosity of the
Cepheid variable star.
B) The recession
velocity of a galaxy is directly proportional to its distance from us.
C) The recession
velocity of a galaxy is inversely proportional to its distance from us.
D) The faster a
spiral galaxy's rotation speed, the more luminous it is.
E) The faster a spiral
galaxy's rotation speed, the less luminous it is.
28) What is the primary practical difficulty that
limits the use of Hubble's law for measuring
distances?
A) Redshifts of
galaxies are difficult to measure.
B) The recession
velocities of distant galaxies are so great that they are hard to measure.
C) We do not know
Hubble's constant very accurately yet.
D) Hubble's law is
only useful theoretically; it is difficult to use in practice.
E) The motion of
the Earth relative to the Milky Way is difficult to account for.
29) How do observations of distant galaxies help
us learn about galaxy evolution?
A) Observations at
different distances show galaxies of different ages and therefore different
stages
of evolution.
B) We can observe
the birth of galaxies.
C) We can observe
the evolution of a single galaxy over time.
D) We can observe
two galaxies merging and what the result is, helping us learn how mergers
affect
evolution.
E) We can see what
our galaxy used to look like and therefore theorize about the physical
processes that led to its current appearance.
30) What is a quasar?
A) a starlike
object that actually represents a bright patch of gas in the Milky Way
B) a very large
galaxy thought to be formed by the merger of several smaller galaxies,
typically found in the center of a galaxy
cluster
C) a specialized
astronomical instrument for observing distant stars.
D) the extremely
bright center of a distant galaxy, thought to be powered by a massive black
hole
E) another name
for very bright stars of spectral type O
1) Answer: A
2) Answer: C
3) Answer: B
4) Answer: C
5) Answer: D
6) Answer: C
7) Answer: E
8) Answer: A
9) Answer: D
10) Answer: A
11) Answer: B
12) Answer: E
13) Answer: B
14) Answer: B
15) Answer: A
16) Answer: C
17) Answer: B
18) Answer: E
19) Answer: C
20) Answer: C
21) Answer: C
22) Answer: C
23) Answer: E
24) Answer: E
25) Answer: B
26) Answer: D
27) Answer: B
28) Answer: C
29) Answer: A
30) Answer: D