b stars in that direction are obscured by interstellar gas.. c stars in that direction are obscured by interstellar dust.. b stars in that direction are obscured by interstellar gas.. As
Trang 2Some 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
© 2017 Pearson Education, Inc.
Trang 3Some 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.
d) numerous black holes capture all the starlight behind them
Explanation: Dust
grains are about
the same size as
visible light, and they can scatter or block the shorter wavelengths
Trang 4When 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
© 2017 Pearson Education, Inc.
Trang 5When a star’s visible light passes through interstellar dust, the light we see
b) appears to twinkle
c) is Doppler shifted
d) turns bluish in color
e) ionizes the dust and
creates emission lines
Explanation: The same process results in wonderful sunsets, as dust in the air scatters the Sun’s blue light, leaving dimmer, redder light
Trang 6Astronomers 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
© 2017 Pearson Education, Inc.
Trang 7Astronomers 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
are correct.
Explanation: Nebula refers
to any fuzzy patch—bright or
dark—in the sky
Trang 8Interstellar gas is composed primarily of
a) 90% hydrogen, 9% helium, and 1% heavier elements
b) molecules including water and CO2.
c) 50% hydrogen and 50% helium
d) hydrogen, oxygen, and nitrogen
e) 99% hydrogen and 1% heavier elements
© 2017 Pearson Education, Inc.
Trang 9Interstellar gas is composed primarily of
b) molecules including water and CO2.
c) 50% hydrogen and 50% helium
d) hydrogen, oxygen, and nitrogen
e) 99% hydrogen and 1% heavier elements
Explanation: The composition of
interstellar gas mirrors that of the
Sun, stars, and the jovian planets
Trang 10The reddish color of emission nebulae indicates that
a) gas and dust are 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
© 2017 Pearson Education, Inc.
Trang 11The reddish color of emission nebulae indicates that
a) gas and dust are moving away from Earth
c) dying stars have recently exploded
d) cool red stars are hidden inside
e) dust is present
Explanation: Glowing hydrogen
gas emits red light around the
Horsehead Nebula
Trang 12Twenty-one-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
© 2017 Pearson Education, Inc.
Trang 13Twenty-one-centimeter radiation is important because
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
Explanation: Cool atomic
hydrogen gas produces 21-cm
radio radiation as its electron
“flips” its direction of spin
Trang 14Complex 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
© 2017 Pearson Education, Inc.
Trang 15Complex molecules in space are found
a) in the photospheres of red giant stars
c) in the coronas of stars like our Sun
d) scattered evenly throughout interstellar space
e) surrounding energetic young stars
Explanation: A radio telescope image of the outer portion of the Milky Way reveals molecular cloud complexes
Trang 16Stars are often born within groups known as
Trang 17Stars are often born within groups known as
Trang 18Very young stars in small clusters of 10–100 members are known as
Trang 19Very young stars in small clusters of 10–100 members are known as
newborn cluster of hot young
blue type O and B stars—a
perfect OB association
Trang 20All stars in a stellar cluster have roughly the same
Trang 21All stars in a stellar cluster have roughly the same
Trang 22Globular clusters are typically observed
a) in the plane of our Galaxy
b) above or below the plane of our Galaxy
c) near our Sun
d) in the hearts of other
galaxies
© 2017 Pearson Education, Inc.
Trang 23Globular clusters are typically observed
a) in the plane of our Galaxy
c) near our Sun
d) in the hearts of other
galaxies
Explanation: Globular clusters
orbit the center of the Milky
Way and are usually seen
above or below the galactic
plane far from our Sun
Trang 24Stars in clusters and associations have about the same
Trang 25Stars in clusters and associations have about the same
Explanation: 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
Trang 26Objects 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
© 2017 Pearson Education, Inc.
Trang 27Objects more massive than our Sun form into stars
a) much slower, over billions of years
b) in about the same time
thousands of years.
d) not at all—they are unstable
Explanation:
More mass → faster collapse
More mass → faster start of fusion reactions
More mass → a hotter, more luminous main-sequence star
Trang 28How 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, and comets
c) Clouds rotate and throw off mass until only enough is left to form one star
© 2017 Pearson Education, Inc.
Trang 29How do single stars form within huge clouds of interstellar gas and dust?
b) One star forms; other matter goes into planets, moons, asteroids, and comets
c) Clouds rotate and throw off mass until only enough is left
to form one star
Explanation: The theory
of star formation predicts
stars in a cluster would
form about the same time
Trang 30What is a T-Tauri 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
© 2017 Pearson Education, Inc.
Trang 31What is a T-Tauri 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
a star
Explanation: T-Tauri stars often show
jets of gas emitted in two directions—
bipolar flow—suggesting they are not
yet stable
Trang 32A 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
© 2017 Pearson Education, Inc.
Trang 33A key feature of globular clusters is that they have
a) very few cool stars
c) lots of massive main-sequence stars
d) stars with very different ages
e) high concentrations of metals
Explanation: The H–R diagram of a
globular cluster has a low “turnoff
point,” indicating its extreme age