Question 1

What kinds of objects lie in the disk of our galaxy?

Accepted Answer

A) open clusters 
B) O and B stars 
C) old K and M stars 
D) gas and dust 
E) all of the above 
A) open clusters 
B) O and B stars 
C) old K and M stars 
D) gas and dust 
E) all of the above

Question 2

Suppose you discovered a star made purely of hydrogen and helium.How old do you think it would be? Explain.

Accepted Answer

A star made of only helium and hydrogen

Question 3

Sound waves in space

Accepted Answer

A) do not exist. 
B) travel so slowly that they are unnoticeable. 
C) travel much faster than sound on Earth but have such low density that they are inaudible. 
D) travel much faster than sound on Earth and are therefore very loud. 
E) can travel through the halo but not the disk of the galaxy. 
A) do not exist. 
B) travel so slowly that they are unnoticeable. 
C) travel much faster than sound on Earth but have such low density that they are inaudible. 
D) travel much faster than sound on Earth and are therefore very loud. 
E) can travel through the halo but not the disk of the galaxy.

Question 4

Suppose you read somewhere that 10 percent of the matter in the Milky Way is in the form of dust grains.Should you be surprised? If so,why?

Accepted Answer

A) There is nothing surprising about 10 percent of the matter being dust grains because dust grains are the material from which stars are born. 
B) Given how easily dust grains form,10 percent is a surprisingly low fraction of material to be in that form. 
C) Ten percent is surprisingly high because dust grains can form only at low temperatures. 
D) The 10 percent figure cannot be correct,because dust grains are solid but only about 2 percent of the matter in our galaxy is made of anything besides hydrogen and helium. 
A) There is nothing surprising about 10 percent of the matter being dust grains because dust grains are the material from which stars are born. 
B) Given how easily dust grains form,10 percent is a surprisingly low fraction of material to be in that form. 
C) Ten percent is surprisingly high because dust grains can form only at low temperatures. 
D) The 10 percent figure cannot be correct,because dust grains are solid but only about 2 percent of the matter in our galaxy is made of anything besides hydrogen and helium.

Question 5

What evidence suggests that the protogalactic cloud that formed the Milky Way resulted from several collisions among smaller clouds?

Accepted Answer

A) The stars in the halo of the Milky Way are organized into several dense clusters arranged throughout the halo. 
B) The Milky Way resembles an elliptical galaxy more than other spirals do. 
C) Halo stars differ in age and heavy-element content,but these variations do not seem to depend on the stars' distance from the galactic center. 
D) The bulge of the Milky Way is surrounded by many globular clusters,just as elliptical galaxies are. 
E) The Milky Way is the central galaxy of a cluster of galaxies. 
A) The stars in the halo of the Milky Way are organized into several dense clusters arranged throughout the halo. 
B) The Milky Way resembles an elliptical galaxy more than other spirals do. 
C) Halo stars differ in age and heavy-element content,but these variations do not seem to depend on the stars' distance from the galactic center. 
D) The bulge of the Milky Way is surrounded by many globular clusters,just as elliptical galaxies are. 
E) The Milky Way is the central galaxy of a cluster of galaxies.

Question 6

How should we expect the Milky Way's interstellar medium to be different in 50 billion years than it is today?

Accepted Answer

A) The total amount of gas will be about the same,but it will contain a much higher percentage of elements heavier than hydrogen and helium. 
B) The total amount of gas will be much less than it is today. 
C) The total amount of gas will be much greater,since many stars will undergo supernovae between now and then. 
D) Thanks to the recycling of the star-gas-star cycle,the interstellar medium should look about the same in 50 billion years as it does today. 
A) The total amount of gas will be about the same,but it will contain a much higher percentage of elements heavier than hydrogen and helium. 
B) The total amount of gas will be much less than it is today. 
C) The total amount of gas will be much greater,since many stars will undergo supernovae between now and then. 
D) Thanks to the recycling of the star-gas-star cycle,the interstellar medium should look about the same in 50 billion years as it does today.

Question 7

Where do most dust grains form?

Accepted Answer

A) in supernovae 
B) in the winds of red giant stars 
C) in planetary nebulae 
D) in molecular clouds 
E) all of the above 
A) in supernovae 
B) in the winds of red giant stars 
C) in planetary nebulae 
D) in molecular clouds 
E) all of the above

Question 8

How did star formation likely proceed in the protogalactic cloud that formed the Milky Way?

Accepted Answer

A) The stars that formed first eventually settled into a galactic disk,circling the center of the galaxy. 
B) The protogalactic cloud gradually formed stars,starting from the center of the galaxy working outwards. 
C) The stars that formed first could orbit the center of the galaxy in any direction at any inclination. 
D) The protogalactic cloud gradually formed stars,starting from the outer edges of the spiral arms and working inward. 
A) The stars that formed first eventually settled into a galactic disk,circling the center of the galaxy. 
B) The protogalactic cloud gradually formed stars,starting from the center of the galaxy working outwards. 
C) The stars that formed first could orbit the center of the galaxy in any direction at any inclination. 
D) The protogalactic cloud gradually formed stars,starting from the outer edges of the spiral arms and working inward.

Question 9

What is the diameter of the disk of the Milky Way?

Accepted Answer

A) 100 light-years 
B) 1,000 light-years 
C) 10,000 light-years 
D) 100,000 light-years 
E) 1,000,000 light-years 
A) 100 light-years 
B) 1,000 light-years 
C) 10,000 light-years 
D) 100,000 light-years 
E) 1,000,000 light-years

Question 10

Nebulae that scatter light are bluer than the stars that illuminate them.Earth's sky is bluer than the Sun.Is this a coincidence? Explain why or why not.

Accepted Answer

Nebulae that scatter light are bluer tha

Question 11

How does the interstellar medium affect our view of most of the galaxy?

Accepted Answer

A) It prevents us from seeing most of the galactic disk with visible and ultraviolet light. 
B) It absorbs all wavelengths of light. 
C) It produces so much visible light that it blocks our view of anything beyond it. 
D) It has no effect on visible-light observations,but prevents us from studying the galactic center with radio waves or X-rays. 
A) It prevents us from seeing most of the galactic disk with visible and ultraviolet light. 
B) It absorbs all wavelengths of light. 
C) It produces so much visible light that it blocks our view of anything beyond it. 
D) It has no effect on visible-light observations,but prevents us from studying the galactic center with radio waves or X-rays.

Question 12

Which of the following analogies best describes how the structure of the galaxy's spiral arms is maintained?

Accepted Answer

A) Like military jets flying in formation above a football stadium,the stars in the spiral arms keep a spiral-shaped formation as they orbit the galaxy. 
B) Like cars slowing in traffic to look at an accident,stars slow as they pass through the spiral arms. 
C) Like a coiling rope,the spiral arms wind up tighter with every galactic rotation. 
D) Like the fins of a giant pinwheel toy,the spiral arms carry a set of bright stars around as they sweep through the galaxy. 
A) Like military jets flying in formation above a football stadium,the stars in the spiral arms keep a spiral-shaped formation as they orbit the galaxy. 
B) Like cars slowing in traffic to look at an accident,stars slow as they pass through the spiral arms. 
C) Like a coiling rope,the spiral arms wind up tighter with every galactic rotation. 
D) Like the fins of a giant pinwheel toy,the spiral arms carry a set of bright stars around as they sweep through the galaxy.

Question 13

What is a superbubble?

Accepted Answer

A) a very low-density region of interstellar space,formed by the merger of several bubbles 
B) a very high-density region of interstellar space,filled with gas ejected from nearby star systems 
C) a bubble so large that it fills much of the galactic halo 
D) the region of space cleared by a powerful supernova 
E) a cloud of gas that can form a million or more stars 
A) a very low-density region of interstellar space,formed by the merger of several bubbles 
B) a very high-density region of interstellar space,filled with gas ejected from nearby star systems 
C) a bubble so large that it fills much of the galactic halo 
D) the region of space cleared by a powerful supernova 
E) a cloud of gas that can form a million or more stars

Question 14

Applying the Newton's version of Kepler's third law (or the orbital velocity law)to a star orbiting 40,000 light-years from the center of the Milky Way Galaxy allows us to determine

Accepted Answer

A) the total mass of the entire Milky Way Galaxy. 
B) the mass of the black hole thought to reside in the center of the galaxy. 
C) the percentage of the galaxy's mass that is made of dark matter. 
D) the mass of the Milky Way Galaxy that lies within 40,000 light-years of the galactic center. 
A) the total mass of the entire Milky Way Galaxy. 
B) the mass of the black hole thought to reside in the center of the galaxy. 
C) the percentage of the galaxy's mass that is made of dark matter. 
D) the mass of the Milky Way Galaxy that lies within 40,000 light-years of the galactic center.

Question 15

Process of Science: How did scientists determine the location of the center of the Milky Way,and why had they been wrong in their previous estimate (where they placed the Sun near the center)?

Accepted Answer

They used globular clusters,which are sp

Question 16

Almost all elements heavier than hydrogen and helium were made inside stars.

Accepted Answer

A) True 
 B)False

Question 17

Based on observations,which of the following statements about stars in the Milky Way is generally true?

Accepted Answer

A) The older the star,the bluer its color. 
B) The older the star,the faster its orbital speed. 
C) The older the star,the lower its abundance of heavy elements. 
D) The younger the star,the higher its mass. 
A) The older the star,the bluer its color. 
B) The older the star,the faster its orbital speed. 
C) The older the star,the lower its abundance of heavy elements. 
D) The younger the star,the higher its mass.

Question 18

Most of the halo stars are very old.

Accepted Answer

A) True 
 B)False

Question 19

Most stars in the Milky Way's halo are

Accepted Answer

A) very old. 
B) found inside molecular clouds. 
C) very young. 
D) blue or white in color. 
A) very old. 
B) found inside molecular clouds. 
C) very young. 
D) blue or white in color.

Question 20

What is the most common form of gas in the interstellar medium?

Accepted Answer

A) molecular hydrogen 
B) molecular helium 
C) atomic hydrogen 
D) atomic helium 
E) ionized hydrogen 
A) molecular hydrogen 
B) molecular helium 
C) atomic hydrogen 
D) atomic helium 
E) ionized hydrogen

Exam 19: Our Galaxy

What kinds of objects lie in the disk of our galaxy?

Suppose you discovered a star made purely of hydrogen and helium.How old do you think it would be? Explain.

Sound waves in space

Suppose you read somewhere that 10 percent of the matter in the Milky Way is in the form of dust grains.Should you be surprised? If so,why?

What evidence suggests that the protogalactic cloud that formed the Milky Way resulted from several collisions among smaller clouds?

How should we expect the Milky Way's interstellar medium to be different in 50 billion years than it is today?

Where do most dust grains form?

How did star formation likely proceed in the protogalactic cloud that formed the Milky Way?

What is the diameter of the disk of the Milky Way?

Nebulae that scatter light are bluer than the stars that illuminate them.Earth's sky is bluer than the Sun.Is this a coincidence? Explain why or why not.

How does the interstellar medium affect our view of most of the galaxy?

Which of the following analogies best describes how the structure of the galaxy's spiral arms is maintained?

What is a superbubble?

Applying the Newton's version of Kepler's third law (or the orbital velocity law)to a star orbiting 40,000 light-years from the center of the Milky Way Galaxy allows us to determine

Process of Science: How did scientists determine the location of the center of the Milky Way,and why had they been wrong in their previous estimate (where they placed the Sun near the center)?

Almost all elements heavier than hydrogen and helium were made inside stars.

Based on observations,which of the following statements about stars in the Milky Way is generally true?

Most of the halo stars are very old.

Most stars in the Milky Way's halo are

What is the most common form of gas in the interstellar medium?

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light and Matter: Reading Messages from the Cosmos

Telescopes: Portals of Discovery

Our Planetary System

Formation of the Solar System

Planetary Geology: Earth and the Other Terrestrial Worlds

Planetary Atmospheres: Earth and the Other Terrestrial Worlds

Jovian Planet Systems

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Other Planetary Systems: The New Science of Distant Worlds

Our Star

Surveying the Stars

Star Birth

Star Stuff

The Bizarre Stellar Graveyard

Galaxies and the Foundations of Modern Cosmology

Galaxy Evolution

The Birth of the Universe

Dark Matter, Dark Energy, and the Fate of the Universe

Life in the Universe

Celestial Timekeeping and Navigation

Space and Time

Spacetime and Gravity

Building Blocks of the Universe

Filters