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Questions
Chapter 12
Stellar Evolution
Copyright © 2010 Pearson Education, Inc.
Question 1
Stars like our
Sun will end
their lives as
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a) red giants.
b) pulsars.
c) black holes.
d) white dwarfs.
e) red dwarfs.
Question 1
Stars like our
Sun will end
their lives as
a) red giants.
b) pulsars.
c) black holes.
d) white dwarfs.
e) red dwarfs.
Low-mass stars eventually
swell into red giants, and
their cores later contract
into white dwarfs.
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Question 2
Elements heavier than
hydrogen and Helium
were created
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a) in the Big Bang.
b) by nucleosynthesis in massive stars.
c) in the cores of stars like the Sun.
d) within planetary nebulae.
e) They have always existed.
Question 2
Elements heavier than
hydrogen and helium
were created
a) in the Big Bang.
b) by nucleosynthesis in massive stars.
c) in the cores of stars like the Sun.
d) within planetary nebula
e) They have always existed.
Massive stars create
enormous core
temperatures as red
supergiants, fusing helium
into carbon, oxygen, and
even heavier elements.
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Question 3
The Sun will
evolve away
from the main
sequence when
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a) its core begins fusing iron.
b) its supply of hydrogen is used up.
c) the carbon core detonates, and it
explodes as a Type I supernova.
d) helium builds up in the core, while the
hydrogen-burning shell expands.
e) the core loses all of its neutrinos, so all
fusion ceases.
Question 3
The Sun will
evolve away
from the main
sequence when
a) its core begins fusing iron.
b) its supply of hydrogen is used up.
c) the carbon core detonates, and it
explodes as a Type I supernova.
d) helium builds up in the core, while the
hydrogen-burning shell expands.
e) the core loses all of its neutrinos, so all
fusion ceases.
When the Sun’s core becomes
unstable and contracts,
additional H fusion generates
extra pressure, and the star
will swell into a red giant.
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Question 4
The helium
flash occurs
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a) when T-Tauri bipolar jets shoot out.
b) in the middle of the main sequence stage.
c) in the red giant stage.
d) during the formation of a neutron star.
e) in the planetary nebula stage.
Question 4
The helium
flash occurs
a) when T-Tauri bipolar jets shoot out.
b) in the middle of the main sequence stage.
c) in the red giant stage.
d) during the formation of a neutron star.
e) in the planetary nebula stage.
When the collapsing core of
a red giant reaches high
enough temperatures and
densities, helium can fuse
into carbon quickly – a
helium flash.
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Question 5
Stars gradually lose
mass as they
become white
dwarfs during the
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a) T-Tauri stage.
b) emission nebula stage.
c) supernova stage.
d) nova stage.
e) planetary nebula stage.
Question 5
Stars gradually lose
mass as they
become white
dwarfs during the
a) T-Tauri stage.
b) emission nebula stage.
c) supernova stage.
d) nova stage.
e) planetary nebula stage.
Low-mass stars forming
white dwarfs slowly lose
their outer atmospheres,
and illuminate these gases
for a relatively short time.
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Question 6
Astronomers
determine the age
of star clusters by
observing
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a) the number of main sequence stars.
b) the ratio of giants to supergiants.
c) the luminosity of stars at the turnoff
point.
d) the number of white dwarfs.
e) supernova explosions.
Question 6
Astronomers
determine the age
of star clusters by
observing
a) the number of main sequence stars.
b) the ratio of giants to supergiants.
c) the luminosity of stars at the turnoff
point.
d) the number of white dwarfs.
e) supernova explosions.
The H–R diagram of a cluster can
indicate its approximate age.
Turnoff point from the main
sequence
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Question 7
The source of
pressure that
makes a white
dwarf stable is
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a) electron degeneracy.
b) neutron degeneracy.
c) thermal pressure from intense core
temperatures.
d) gravitational pressure.
e) helium-carbon fusion.
Question 7
The source of
pressure that
makes a white
dwarf stable is
a) electron degeneracy.
b) neutron degeneracy.
c) thermal pressure from intense core
temperatures.
d) gravitational pressure.
e) helium-carbon fusion.
Electrons in the core cannot
be squeezed infinitely close,
and prevent a low-mass star
from collapsing further.
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Question 8
In a white dwarf,
the mass of the
Sun is packed into
the volume of
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a) an asteroid.
b) a planet the size of Earth.
c) a planet the size of Jupiter.
d) an object the size of the Moon.
e) an object the size of a sugar cube.
Question 8
In a white dwarf,
the mass of the
Sun is packed into
the volume of
a) an asteroid.
b) a planet the size of Earth.
c) a planet the size of Jupiter.
d) an object the size of the Moon.
e) an object the size of a sugar cube.
The density of a white
dwarf is about a million
times greater than normal
solid matter.
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Question 9
In a young star
cluster, when more
massive stars are
evolving into red
giants, the least
massive stars are
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a) ending their main-sequence stage.
b) also evolving into red giants.
c) forming planetary nebulae.
d) barely starting to fuse hydrogen.
e) starting the nova stage.
Question 9
In a young star
cluster, when more
massive stars are
evolving into red
giants, the least
massive stars are
a) ending their main-sequence stage.
b) also evolving into red giants.
c) forming planetary nebulae.
d) barely starting to fuse hydrogen.
e) starting the nova stage.
More massive stars form much
faster, and have much shorter
main-sequence lifetimes.
Low-mass stars form more
slowly.
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Question 10
A star will spend
most of its
“shining” lifetime
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a) as a protostar.
b) as a red giant.
c) as a main-sequence star.
d) as a white dwarf.
e) evolving from type O to type M.
Question 10
A star will spend
most of its
“shining” lifetime
a) as a protostar.
b) as a red giant.
c) as a main-sequence star.
d) as a white dwarf.
e) evolving from type O to type M.
In the main-sequence stage,
hydrogen fuses to helium.
Pressure from light and
heat pushing out balances
gravitational pressure
pushing inward.
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Question 11
A nova
involves
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a) mass transfer onto a white dwarf in a binary
star system.
b) repeated helium fusion flashes in red giants.
c) rapid collapse of a protostar into a massive O
star.
d) the explosion of a low-mass star.
e) the birth of a massive star in a new cluster.
Question 11
A nova
involves
a) mass transfer onto a white dwarf in a binary
star system.
b) repeated helium fusion flashes in red giants.
c) rapid collapse of a protostar into a massive O
star.
d) the explosion of a low-mass star.
e) the birth of a massive star in a new cluster.
Sudden, rapid fusion of new
fuel dumped onto a white
dwarf causes the star to flare
up, and for a short time
become much brighter.
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Question 12
What type of atomic
nuclei heavier than
helium are most
common, and why?
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a) those heavier than iron, because
of supernovae
b) iron, formed just before massive
stars explode
c) odd-numbered nuclei, built with
hydrogen fusion
d) even-numbered nuclei, built with
helium fusion
Question 12
What type of atomic
nuclei heavier than
helium are most
common, and why?
a) those heavier than iron, because
of supernovae
b) iron, formed just before massive
stars explode
c) odd-numbered nuclei, built with
hydrogen fusion
d) even-numbered nuclei, built with
helium fusion
Helium nuclei have an atomic
mass of 4; they act as building
blocks in high-temperature
fusion within supergiants.
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Question 13
A white dwarf
can explode
when
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a) its mass exceeds the Chandrasekhar limit.
b) its electron degeneracy increases
enormously.
c) fusion reactions increase in it’s core.
d) iron in its core collapses.
e) the planetary nebula stage ends.
Question 13
A white dwarf
can explode
when
a) its mass exceeds the Chandrasekhar limit.
b) its electron degeneracy increases
enormously.
c) fusion reactions increase in it’s core.
d) iron in its core collapses.
e) the planetary nebula stage ends.
If additional mass from a companion star pushes a white dwarf
beyond 1.4 solar masses, it can explode in a Type I supernova.
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Question 14
A Type II
supernova
occurs when
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a) hydrogen fusion shuts off.
b) uranium decays into lead.
c) iron in the core starts to fuse.
d) helium is exhausted in the outer layers.
e) a white dwarf gains mass.
Question 14
A Type II
supernova
occurs when
a) hydrogen fusion shuts off.
b) uranium decays into lead.
c) iron in the core starts to fuse.
d) helium is exhausted in the outer layers.
e) a white dwarf gains mass.
Fusion of iron does not produce energy or provide pressure; the
star’s core collapses immediately, triggering a supernova explosion.
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Question 15
Supernova
1987A was
important
because
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a) its parent star had been studied before
the explosion.
b) its distance was already known.
c) it was observed early, as its light was
still increasing.
d) its evolution was captured with detailed
images from the Hubble Space
Telescope.
e) All of the above are true.
Question 15
Supernova
1987A was
important
because
a) its parent star had been studied before
the explosion.
b) its distance was already known.
c) it was observed early, as its light was
still increasing.
d) its evolution was captured with detailed
images from the Hubble Space
Telescope.
e) All of the above are true.
Supernovae are important distance
indicators in the study of galaxies
beyond the Milky Way.
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Question 16
As stars
evolve during
their mainsequence
lifetime
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a) they gradually become cooler and
dimmer (spectral type O to type M).
b) they gradually become hotter and
brighter (spectral type M to type O).
c) they don’t change their spectral type.
Question 16
As stars
evolve during
their mainsequence
lifetime
a) they gradually become cooler and
dimmer (spectral type O to type M).
b) they gradually become hotter and
brighter (spectral type M to type O).
c) they don’t change their spectral type.
A star’s main-sequence characteristics of surface
temperature and brightness are based on its mass.
Stars of different initial mass become different spectral
types on the main sequence.
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Question 17
More massive
white dwarfs are
______ compared
with less massive
white dwarfs.
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a) hotter
b) smaller
c) larger
d) cooler
e) identical in size
Question 17
More massive
white dwarfs are
______ compared
with less massive
white dwarfs.
a) hotter
b) smaller
c) larger
d) cooler
e) identical in size
Chandrasekhar showed that more mass will squeeze a
white dwarf into a smaller volume, due to electron
degeneracy pressure.
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