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Chapter 14 Clickers
Astronomy: A Beginner’s
Guide to the Universe
Seventh Edition
The Milky Way
Galaxy
© 2013 Pearson Education, Inc.
Question 1
The location of the galactic center was identified using
a) supernova remnants.
b) white dwarf stars in the spiral arms.
c) red giant variable stars in globular clusters.
d) bright O and B stars in open clusters.
e) X-ray sources.
© 2013 Pearson Education, Inc.
Question 1
The location of the galactic center was identified using
a) supernova remnants.
b) white dwarf stars in the spiral arms.
c) red giant variable stars in globular clusters.
d) bright O and B stars in open clusters.
e) X-ray sources.
Explanation:
Harlow Shapley used pulsating RR-Lyrae
variables as distance indicators to the
globular clusters.
He then deduced the distance and direction
of the Milky Way’s center.
© 2013 Pearson Education, Inc.
Question 2
Our Sun is located in the Milky Way Galaxy
a) about 30 Kpc from the center in the halo.
b) 30,000 light-years from the center in a globular cluster.
c) at the outer edge of the galactic disk, in the plane.
d) about halfway from the center, in the spiral arms.
e) in the bulge, near the Orion arm.
© 2013 Pearson Education, Inc.
Question 2
Our Sun is located in the Milky Way Galaxy
a) about 30 Kpc from the center in the halo.
b) 30,000 light-years from the center in a globular cluster.
c) at the outer edge of the galactic disk, in the plane.
d) about halfway from the center, in the spiral arms.
e) in the bulge, near the Orion arm.
Explanation:
The Sun orbits the center of the Galaxy
within the disk, taking about 225 million
years to complete one orbit.
© 2013 Pearson Education, Inc.
Question 3
The period – luminosity relationship is a crucial component of
a) measuring distances with Cepheid variable stars.
b) identifying the mass of the Galaxy’s central black hole.
c) determining the masses of stars in an eclipsing binary system.
d) using spectroscopic parallax to measure distances to stars.
© 2013 Pearson Education, Inc.
Question 3
The period – luminosity relationship is a crucial component of
a) measuring distances with Cepheid variable stars.
b) identifying the mass of the Galaxy’s central black hole.
c) determining the masses of stars in an eclipsing binary system.
d) using spectroscopic parallax to measure distances to stars.
Explanation:
Cepheid variable stars with
longer periods have higher actual
luminosities; short-period Cepheids
are dimmer.
© 2013 Pearson Education, Inc.
Question 4
High-speed motion of gas and stars near the Milky Way
Galaxy’s center is explained by
a) tidal forces from the Andromeda Galaxy.
b) accretion disks around neutron stars.
c) gamma-ray bursts.
d) gravitation from globular clusters.
e) a supermassive black hole.
© 2013 Pearson Education, Inc.
Question 4
High-speed motion of gas and stars near the Milky Way
Galaxy’s center is explained by
a) tidal forces from the Andromeda Galaxy.
b) accretion disks around neutron stars.
c) gamma-ray bursts.
d) gravitation from globular clusters.
e) a supermassive black hole.
Explanation:
Recent observations
estimate the black hole to be
4 million solar masses.
© 2013 Pearson Education, Inc.
Question 5
Detailed measurements of the disk suggest that our
Milky Way is
a) a spiral galaxy.
b) a barred spiral galaxy.
c) an elliptical galaxy.
d) a quasar.
e) an irregular galaxy.
© 2013 Pearson Education, Inc.
Question 5
Detailed measurements of the disk suggest that our
Milky Way is
a) a spiral galaxy.
b) a barred spiral galaxy.
c) an elliptical galaxy.
d) a quasar.
e) an irregular galaxy.
Explanation:
Measurements of stellar motion in and
near the bulge imply that it is football
shaped, about half as wide as it is long,
characteristic of a barred spiral galaxy.
© 2013 Pearson Education, Inc.
Question 6
What two observations allow us to estimate the Galaxy’s
mass?
a) the Sun’s mass and velocity in orbit around the galactic
center
b) the rotation of the bulge and disk components
c) the Sun’s age and age of the globular cluster stars
d) the motion of spiral arms and the mass of the central black
hole
e) the orbital period and distance from the galactic center of
objects near the edge of the Galaxy
© 2013 Pearson Education, Inc.
Question 6
What two observations allow us to estimate the Galaxy’s
mass?
a) the Sun’s mass and velocity in orbit around the galactic
center
b) the rotation of the bulge and disk components
c) the Sun’s age and age of the globular cluster stars
d) the motion of spiral arms and the mass of the central black
hole
e) the orbital period and distance from the galactic center of
objects near the edge of the Galaxy
Explanation:
Use the modified form of Kepler’s law to find the mass:
Total mass = (orbital size)3 / (orbital period)2
© 2013 Pearson Education, Inc.
Question 7
In the formation of our Galaxy
a) the spiral arms formed first.
b) the globular clusters formed first.
c) the disk component started out thin and grew.
d) spiral density waves formed first.
e) the bar in the bulge formed first.
© 2013 Pearson Education, Inc.
Question 7
In the formation of our Galaxy
a) the spiral arms formed first.
b) the globular clusters formed first.
c) the disk component started out thin and grew.
d) spiral density waves formed first.
e) the bar in the bulge formed first.
Explanation:
Globular clusters contain very old
stars, no gas or dust, and orbit
around the center randomly.
© 2013 Pearson Education, Inc.
Question 8
21-cm radio radiation is useful in studying our Galaxy
because
a) the waves penetrate dusty cocoons to reveal star
formation.
b) it reflects from the Galaxy’s core.
c) the waves are not absorbed by galactic black holes.
d) it can be used to map out the cool hydrogen in spiral
arms.
e) radio waves provide a distance measurement like parallax.
© 2013 Pearson Education, Inc.
Question 8
21-cm radio radiation is useful in studying our Galaxy
because
a) the waves penetrate dusty cocoons to reveal star
formation.
b) it reflects from the Galaxy’s core.
c) the waves are not absorbed by galactic black holes.
d) it can be used to map out the cool hydrogen in spiral
arms.
e) radio waves provide a distance measurement like parallax.
Explanation:
The Doppler shifts of 21-cm radiation from hydrogen in the spiral arms
provides astronomers with a tool to map out the Galaxy’s structure.
© 2013 Pearson Education, Inc.
Question 9
Which of these is not a typical part of our Galaxy’s
spiral arms?
a) OB associations
b) open clusters
c) giant molecular clouds
d) emission nebulae
e) globular clusters
© 2013 Pearson Education, Inc.
Question 9
Which of these is not a typical part of our Galaxy’s
spiral arms?
a) OB associations
b) open clusters
c) giant molecular clouds
d) emission nebulae
e) globular clusters
Explanation:
The spiral arms contain gas,
dust, molecular clouds, new
clusters, and Population I stars.
© 2013 Pearson Education, Inc.
Question 10
What suggests that the mass of our Galaxy extends
farther than its visible disk?
a) 21-cm maps of the spiral arms
b) the rotation curve of the outer edges of the Galaxy
c) orbits of open clusters in the disk
d) infrared observations of new star- forming regions
e) X-ray images of other galaxies
© 2013 Pearson Education, Inc.
Question 10
What suggests that the mass of our Galaxy extends
farther than its visible disk?
a) 21-cm maps of the spiral arms
b) the rotation curve of the outer edges of the Galaxy
c) orbits of open clusters in the disk
d) infrared observations of new star- forming regions
e) X-ray images of other galaxies
Explanation:
The outer edges of the Galaxy’s
disk rotate much faster than they
should.
Most of the mass of the Galaxy
must be dark matter.
© 2013 Pearson Education, Inc.