Download Question 1

Astronomy
A BEGINNER’S GUIDE
TO THE UNIVERSE
EIGHTH EDITION
CHAPTER 14
The Milky Way Galaxy
Clickers
© 2017 Pearson Education, Inc.
Question 1
The location of the Galactic center was identified early in
the 20th century 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.
© 2017 Pearson Education, Inc.
Question 1
The location of the Galactic center was identified early in
the 20th century 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.
© 2017 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.
© 2017 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.
© 2017 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.
© 2017 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.
© 2017 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.
© 2017 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.
© 2017 Pearson Education, Inc.
Question 5
Detailed measurements of the disk suggest that our Milky
Way is
a)
b)
c)
d)
e)
a spiral galaxy.
a barred spiral galaxy.
an elliptical galaxy.
a quasar.
an irregular galaxy.
© 2017 Pearson Education, Inc.
Question 5
Detailed measurements of the disk suggest that our Milky
Way is
a)
b)
c)
d)
e)
a spiral galaxy.
a barred spiral galaxy.
an elliptical galaxy.
a quasar.
an irregular galaxy.
Explanation: Measurements
imply the disk has a diameter
about 30 times the disk thickness. Embedded in the
disk are spiral arms and a short bar near the center.
© 2017 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
© 2017 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
© 2017 Pearson Education, Inc.
Question 7
In the formation of our Galaxy, the
a)
b)
c)
d)
e)
spiral arms formed first.
globular clusters formed first.
disk component started out thin and grew.
spiral density waves formed first.
bar in the bulge formed first.
© 2017 Pearson Education, Inc.
Question 7
In the formation of our Galaxy, the
a)
b)
c)
d)
e)
spiral arms formed first.
globular clusters formed first.
disk component started out thin and grew.
spiral density waves formed first.
bar in the bulge formed first.
Explanation: Globular clusters
contain very old stars, no gas
or dust, and orbit around the
center randomly.
© 2017 Pearson Education, Inc.
Question 8
Twenty-one centimeter 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.
© 2017 Pearson Education, Inc.
Question 8
Twenty-one centimeter 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.
© 2017 Pearson Education, Inc.
Question 9
Which of these is NOT a typical part of our Galaxy’s spiral
arms?
a)
b)
c)
d)
e)
OB associations
Open clusters
Giant molecular clouds
Emission nebulae
Globular clusters
© 2017 Pearson Education, Inc.
Question 9
Which of these is NOT a typical part of our Galaxy’s spiral
arms?
a)
b)
c)
d)
e)
OB associations
Open clusters
Giant molecular clouds
Emission nebulae
Globular clusters
Explanation: The spiral arms
contain gas, dust, molecular
clouds, new clusters, and
Population I stars.
© 2017 Pearson Education, Inc.
Question 10
What suggests that the mass of our Galaxy extends farther
than its visible disk?
a)
b)
c)
d)
e)
21-cm maps of the spiral arms
The rotation curve of the outer edges of the Galaxy
Orbits of open clusters in the disk
Infrared observations of new star-forming regions
X-ray images of other galaxies
© 2017 Pearson Education, Inc.
Question 10
What suggests that the mass of our Galaxy extends farther
than its visible disk?
a)
b)
c)
d)
e)
21-cm maps of the spiral arms
The rotation curve of the outer edges of the Galaxy
Orbits of open clusters in the disk
Infrared observations of new star-forming regions
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.
© 2017 Pearson Education, Inc.