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Questions
Chapter 11
The Interstellar
Medium
Copyright © 2010 Pearson Education, Inc.
Question 1
Some regions of
the Milky Way’s
disk appear dark
because
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a) there are no stars there.
b) stars in that direction are obscured
by interstellar gas.
c) stars in that direction are obscured
by interstellar dust.
d) numerous black holes capture all
the starlight behind them.
Question 1
Some regions of
the Milky Way’s
disk appear dark
because
a) there are no stars there.
b) stars in that direction are obscured
by interstellar gas.
c) stars in that direction are obscured
by interstellar dust.
d) numerous black holes capture all
the starlight behind them.
Dust grains are about the same size as visible light, and they can
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Inc.
scatter
or block the shorter wavelengths.
Question 2
When a star’s
visible light
passes through
interstellar dust,
the light we see
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a) is dimmed and reddened.
b) appears to twinkle.
c) is Doppler shifted.
d) turns bluish in color.
e) ionizes the dust and creates
emission lines.
Question 2
When a star’s
visible light
passes through
interstellar dust,
the light we see
a) is dimmed and reddened.
b) appears to twinkle.
c) is Doppler shifted.
d) turns bluish in color.
e) ionizes the dust and creates
emission lines.
The same process results
in wonderful sunsets, as
dust in the air scatters the
Sun’s blue light, leaving
dimmer, redder light.
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Question 3
Astronomers use
the term nebula
to refer to
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a) outer envelopes of dying stars that drift
gently into space.
b) remnants of stars that die by supernova.
c) clouds of gas and dust in interstellar space.
d) distant galaxies seen beyond our Milky Way.
e) All of the above are correct.
Question 3
Astronomers use
the term nebula
to refer to
a) outer envelopes of dying stars that drift
gently into space.
b) remnants of stars that die by supernova.
c) clouds of gas and dust in interstellar space.
d) distant galaxies seen beyond our Milky Way.
e) All of the above are correct.
Nebula refers to any
fuzzy patch – bright or
dark – in the sky.
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Question 4
Interstellar gas
is composed
primarily of
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a) 90% hydrogen, 9% helium, and 1%
heavier elements.
b) molecules including water and CO2.
c) 50% hydrogen, 50% helium.
d) hydrogen, oxygen, and nitrogen.
e) 99% hydrogen, and 1% heavier elements.
Question 4
Interstellar gas
is composed
primarily of
a) 90% hydrogen, 9% helium, and 1%
heavier elements.
b) molecules including water and CO2.
c) 50% hydrogen, 50% helium.
d) hydrogen, oxygen, and nitrogen.
e) 99% hydrogen, and 1% heavier elements.
The composition of
interstellar gas mirrors that
of the Sun, stars, and the
jovian planets.
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Question 5
The reddish color of
emission nebulae
indicates that
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a) gas and dust is moving away
from Earth.
b) hydrogen gas is present.
c) dying stars have recently
exploded.
d) cool red stars are hidden inside.
e) dust is present.
Question 5
The reddish color of
emission nebulae
indicates that
a) gas and dust is moving away
from Earth.
b) hydrogen gas is present.
c) dying stars have recently
exploded.
d) cool red stars are hidden inside.
e) dust is present.
Glowing
hydrogen gas
emits red light
around the
Horsehead
nebula.
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Question 6
21-centimeter
radiation is
important
because
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a) its radio waves pass unaffected through
clouds of interstellar dust.
b) it arises from cool helium gas present
throughout space.
c) it can be detected with optical telescopes.
d) it is produced by protostars.
e) it reveals the structure of new stars.
Question 6
21-centimeter
radiation is
important
because
a) its radio waves pass unaffected through
clouds of interstellar dust.
b) it arises from cool helium gas present
throughout space.
c) it can be detected with optical telescopes.
d) it is produced by protostars.
e) it reveals the structure of new stars.
Cool atomic hydrogen gas
produces 21-cm radio radiation
as its electron “flips” its
direction of spin.
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Question 7
Complex
molecules in
space are
found
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a) in the photospheres of red giant stars.
b) primarily inside dense dust clouds.
c) in the coronas of stars like our Sun.
d) scattered evenly throughout interstellar
space.
e) surrounding energetic young stars.
Question 7
Complex
molecules in
space are
found
a) in the photospheres of red giant stars.
b) primarily inside dense dust clouds.
c) in the coronas of stars like our Sun.
d) scattered evenly throughout interstellar
space.
e) surrounding energetic young stars.
A radio telescope image of the outer portion of the Milky Way,
revealing molecular cloud complexes.
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Question 8
Stars are often born
within groups known as
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a) clans.
b) spiral waves.
c) aggregates.
d) clusters.
e) swarms.
Question 8
Stars are often born
within groups known as
a) clans.
b) spiral waves.
c) aggregates.
d) clusters.
e) swarms.
The Pleiades – a nearby open
cluster – is a group of relatively
young stars about 400 light-years
from the Sun.
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Question 9
Very young stars in small
clusters of 10-100 members
are known as
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a) OB associations.
b) molecular cloud complexes.
c) aggregates.
d) globular clusters.
e) hives.
Question 9
Very young stars in small
clusters of 10-100 members
are known as
a) OB associations.
b) molecular cloud complexes.
c) aggregates.
d) globular clusters.
e) hives.
NGC 3603 is a newborn cluster of hot young blue
Type O and B stars – a perfect OB association.
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Question 10
All stars in a stellar cluster
have roughly the same
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a) temperature.
b) color.
c) distance.
d) mass.
e) luminosity.
Question 10
All stars in a stellar cluster
have roughly the same
a) temperature.
b) color.
c) distance.
d) mass.
e) luminosity.
Stars in the Pleiades cluster vary in temperature, color, mass,
and luminosity, but all lie about 440 light-years away.
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Question 11
Globular clusters are
typically observed
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a) in the plane of our Galaxy.
b) above or below the plane of
our Galaxy.
c) near to our Sun.
d) in the hearts of other
galaxies.
Question 11
Globular clusters are
typically observed
a) in the plane of our Galaxy.
b) above or below the plane of
our Galaxy.
c) near to our Sun.
d) in the hearts of other
galaxies.
Globular clusters orbit the center of the Milky Way, and are usually
seen
aboveInc.or below the galactic plane far from our Sun.
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Pearson Education,
Question 12
Stars in clusters &
associations have about
the same
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a) age.
b) temperature.
c) mass.
d) color.
e) luminosity.
Question 12
Stars in clusters &
associations have about
the same
Most of the stars in a cluster
form about the same time.
Stars in the Omega Centauri
globular cluster are
estimated to be about 14
billion years old.
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a) age.
b) temperature.
c) mass.
d) color.
e) luminosity.
Question 13
Objects more
massive than our
Sun form into
stars
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a) much slower, over billions of years.
b) in about the same time.
c) much faster, over tens of thousands
of years.
d) not at all – they are unstable.
Question 13
Objects more
massive than our
Sun form into
stars
a) much slower, over billions of years.
b) in about the same time.
c) much faster, over tens of thousands
of years.
d) not at all – they are unstable.
More mass  faster collapse
More mass  faster start of
fusion reactions
More mass  a hotter, more
luminous main sequence star
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Question 14
How do single
stars form within
huge clouds of
interstellar gas
and dust?
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a) Clouds fragment into smaller objects,
forming many stars at one time.
b) One star forms; other matter goes into
planets, moons, asteroids, & comets.
c) Clouds rotate & throw off mass until only
enough is left to form one star.
Question 14
How do single
stars form within
huge clouds of
interstellar gas
and dust?
a) Clouds fragment into smaller objects,
forming many stars at one time.
b) One star forms; other matter goes into
planets, moons, asteroids, & comets.
c) Clouds rotate & throw off mass until only
enough is left to form one star.
The theory of star formation predicts stars in a cluster
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Inc.
form about the same time.
Question 15
What is a TTauri star?
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a) a collapsing cloud of gas about to
become a protostar
b) a dying star
c) a cool main sequence star
d) a star releasing a planetary nebula
e) a protostar about to become a star
Question 15
What is a TTauri star?
a) a collapsing cloud of gas about to
become a protostar
b) a dying star
c) a cool main sequence star
d) a star releasing a planetary nebula
e) a protostar about to become a star
T-Tauri stars often show jets of
gas emitted in two directions —
“bipolar flow” — suggesting they
are not yet stable.
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Question 16
A key feature of
globular clusters
is that they have
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a ) very few cool stars.
b) the oldest stars in our Galaxy.
c) lots of massive main sequence stars.
d) stars with very different ages.
e) high concentrations of metals.
Question 16
A key feature of
globular clusters
is that they have
a ) very few cool stars.
b) the oldest stars in our Galaxy.
c) lots of massive main sequence stars.
d) stars with very different ages.
e) high concentrations of metals.
The H–R diagram of a
globular cluster has a low
“turnoff point” indicating
its extreme age.
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