Question 1

About what percentage of the mass of a molecular cloud is in the form of dust?

Accepted Answer

A)  1% 
B)  10% 
C)  50% 
D)  98% 
A)  1% 
B)  10% 
C)  50% 
D)  98%

Question 2

Interstellar dust consists mostly of ________.

Accepted Answer

A)  microscopic particles of carbon and silicon 
B)  ozone "smog" 
C)  hydrogen and helium atoms 
D)  tiny grains of water ice 
E)  the same tiny particles found in household dust 
A)  microscopic particles of carbon and silicon 
B)  ozone "smog" 
C)  hydrogen and helium atoms 
D)  tiny grains of water ice 
E)  the same tiny particles found in household dust

Question 3

Most of the current star formation in the Milky Way occurs in its spiral arms.

Accepted Answer

A) True 
 B)False

Question 4

Why do we believe that most of the mass of the Milky Way is in the form of dark matter?

Accepted Answer

A)  The orbital speeds of stars far from the galactic center are surprisingly high, suggesting that these stars are feeling gravitational effects from unseen matter in the halo. 
B)  Although dark matter emits no visible light, it can be seen with radio wavelengths, and such observations confirm that the halo is full of this material. 
C)  Theoretical models of galaxy formation suggest that a galaxy cannot form unless it has at least 10 times as much matter as we see in the Milky Way disk, suggesting that the halo is full of dark matter. 
D)  Our view of distant galaxies is sometimes obscured by dark blotches in the sky, and we believe these blotches are dark matter located in the halo. 
A)  The orbital speeds of stars far from the galactic center are surprisingly high, suggesting that these stars are feeling gravitational effects from unseen matter in the halo. 
B)  Although dark matter emits no visible light, it can be seen with radio wavelengths, and such observations confirm that the halo is full of this material. 
C)  Theoretical models of galaxy formation suggest that a galaxy cannot form unless it has at least 10 times as much matter as we see in the Milky Way disk, suggesting that the halo is full of dark matter. 
D)  Our view of distant galaxies is sometimes obscured by dark blotches in the sky, and we believe these blotches are dark matter located in the halo.

Question 5

What do we mean by the star-gas-star cycle?

Accepted Answer

A)  It is the continuous recycling of gas in the galactic disk between stars and the interstellar medium. 
B)  It is the idea that stars in close binary systems can exchange gas with one another. 
C)  It is the set of nuclear reactions by which heavy elements are produced in the cores of massive stars. 
D)  It describes the orbits of the stars and interstellar medium around the center of the galaxy. 
A)  It is the continuous recycling of gas in the galactic disk between stars and the interstellar medium. 
B)  It is the idea that stars in close binary systems can exchange gas with one another. 
C)  It is the set of nuclear reactions by which heavy elements are produced in the cores of massive stars. 
D)  It describes the orbits of the stars and interstellar medium around the center of the galaxy.

Question 6

How do we know the total mass of the Milky Way Galaxy that is contained within the Sun's orbital path?

Accepted Answer

A)  By applying Newton's version of Kepler's third law (or the equivalent orbital velocity law) to the Sun's orbit around the center of the Galaxy 
B)  By counting the number of stars visible in this region of the galaxy 
C)  By estimating the amount of gas and dust in between the stars 
D)  By using the law of conservation of angular momentum to calculate the orbital speeds of nearby stars 
A)  By applying Newton's version of Kepler's third law (or the equivalent orbital velocity law) to the Sun's orbit around the center of the Galaxy 
B)  By counting the number of stars visible in this region of the galaxy 
C)  By estimating the amount of gas and dust in between the stars 
D)  By using the law of conservation of angular momentum to calculate the orbital speeds of nearby stars

Question 7

Briefly describe the star-gas-star cycle.

Accepted Answer

During a star's lifetime, it fuses hydro

Question 8

What is the best evidence for a supermassive black hole in the center of the Milky Way Galaxy?

Accepted Answer

A)  Amazing filaments of radio emission swirling around the center of the galaxy 
B)  The existence of the Milky Way itself: the mass of the black hole is essential to gravitationally bind the galaxy together, so it doesn't fly apart. 
C)  The gigantic bursts of X-ray energy from a mysterious dark object 
D)  The motions of stars around a mysterious dark object 
A)  Amazing filaments of radio emission swirling around the center of the galaxy 
B)  The existence of the Milky Way itself: the mass of the black hole is essential to gravitationally bind the galaxy together, so it doesn't fly apart. 
C)  The gigantic bursts of X-ray energy from a mysterious dark object 
D)  The motions of stars around a mysterious dark object

Question 9

Harlow Shapley concluded that the Sun was not located at the center of the Milky Way Galaxy by

Accepted Answer

A)  looking at the shape of the "milky band" across the sky. 
B)  mapping the distribution of stars in the galaxy. 
C)  mapping the distribution of globular clusters in the galaxy. 
D)  mapping the distribution of gas clouds in the spiral arms. 
E)  looking at other nearby spiral galaxies. 
A)  looking at the shape of the "milky band" across the sky. 
B)  mapping the distribution of stars in the galaxy. 
C)  mapping the distribution of globular clusters in the galaxy. 
D)  mapping the distribution of gas clouds in the spiral arms. 
E)  looking at other nearby spiral galaxies.

Question 10

Which kind of star is highly unlikely to be found in the halo of the Milky Way?

Accepted Answer

A)  G star 
B)  M star 
C)  K star 
D)  O star 
A)  G star 
B)  M star 
C)  K star 
D)  O star

Question 11

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

Question 12

Where does most star formation occur in the Milky Way Galaxy?

Accepted Answer

A)  In the spiral arms 
B)  Everywhere throughout the galactic disk 
C)  In the central bulge 
D)  Within the halo 
A)  In the spiral arms 
B)  Everywhere throughout the galactic disk 
C)  In the central bulge 
D)  Within the halo

Question 13

Suppose a scientist holds a press conference at which he claims that 10% of the matter in the Milky Way is in the form of dust grains. Does his claim seem reasonable? Why or why not?

Accepted Answer

A)  The 10% figure is too high because there are not enough heavy elements to make that much dust. 
B)  It is reasonable because we already know that interstellar dust obscures our view through the disk of the galaxy. 
C)  The 10% figure is too low because most of the mass of the galaxy is in the form of interstellar dust. 
D)  It seems reasonable as long as we assume that red giant stars-which produce dust grains in their stellar winds-are more common than we thought. 
A)  The 10% figure is too high because there are not enough heavy elements to make that much dust. 
B)  It is reasonable because we already know that interstellar dust obscures our view through the disk of the galaxy. 
C)  The 10% figure is too low because most of the mass of the galaxy is in the form of interstellar dust. 
D)  It seems reasonable as long as we assume that red giant stars-which produce dust grains in their stellar winds-are more common than we thought.

Question 14

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 15

What kind of object do we think lies in the center of the Milky Way Galaxy?

Accepted Answer

A)  A 3 to 4 million solar mass black hole 
B)  A gigantic X-ray binary system 
C)  A dense cluster of young, hot stars 
D)  An enormous collection of dark matter, explaining why we detect no light at all from the galactic center 
A)  A 3 to 4 million solar mass black hole 
B)  A gigantic X-ray binary system 
C)  A dense cluster of young, hot stars 
D)  An enormous collection of dark matter, explaining why we detect no light at all from the galactic center

Question 16

The average speed of stars relative to the Sun in the solar neighborhood is about 20 km/s. Suppose you discover a star in the solar neighborhood that is moving relative to the Sun at a much higher speed, say 220 km/s. What kind of orbit does this star probably have around the Milky Way? In what part of the galaxy does it spend most of its time? Explain.

Accepted Answer

Since stars that are traveling along wit

Question 17

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 18

What is the best evidence for an extremely massive black hole in the center of the Milky Way?

Accepted Answer

A)  The orbits of stars in the center of the galaxy indicate that the presence of 3 to 4 million solar mass object in a region no larger than our Solar System. 
B)  Huge amounts of X-rays are pouring out of the center of the galaxy. 
C)  The center of our galaxy hosts a pulsar that is spinning so fast that it could only be a black hole. 
D)  We observe stars vanishing in the center of the Galaxy as they are sucked into the black hole. 
A)  The orbits of stars in the center of the galaxy indicate that the presence of 3 to 4 million solar mass object in a region no larger than our Solar System. 
B)  Huge amounts of X-rays are pouring out of the center of the galaxy. 
C)  The center of our galaxy hosts a pulsar that is spinning so fast that it could only be a black hole. 
D)  We observe stars vanishing in the center of the Galaxy as they are sucked into the black hole.

Question 19

Observing our galaxy at radio wavelengths allows us to see through the dust in the disk that obscures our view.

Accepted Answer

A) True 
 B)False

Question 20

Sound waves in the interstellar medium

Accepted Answer

A)  cannot travel through the gas. 
B)  travel so slowly that they are undetectable. 
C)  can travel through the gas, but the very low density of the interstellar medium makes them inaudible. 
D)  travel extremely quickly and are therefore very loud. 
E)  can travel through the halo interstellar medium but not the disk of the galaxy. 
A)  cannot travel through the gas. 
B)  travel so slowly that they are undetectable. 
C)  can travel through the gas, but the very low density of the interstellar medium makes them inaudible. 
D)  travel extremely quickly and are therefore very loud. 
E)  can travel through the halo interstellar medium but not the disk of the galaxy.

About what percentage of the mass of a molecular cloud is in the form of dust?

Interstellar dust consists mostly of ________.

Most of the current star formation in the Milky Way occurs in its spiral arms.

Why do we believe that most of the mass of the Milky Way is in the form of dark matter?

What do we mean by the star-gas-star cycle?

How do we know the total mass of the Milky Way Galaxy that is contained within the Sun's orbital path?

Briefly describe the star-gas-star cycle.

What is the best evidence for a supermassive black hole in the center of the Milky Way Galaxy?

Harlow Shapley concluded that the Sun was not located at the center of the Milky Way Galaxy by

Which kind of star is highly unlikely to be found in the halo of the Milky Way?

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

Where does most star formation occur in the Milky Way Galaxy?

Suppose a scientist holds a press conference at which he claims that 10% of the matter in the Milky Way is in the form of dust grains. Does his claim seem reasonable? Why or why not?

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

What kind of object do we think lies in the center of the Milky Way Galaxy?

Most stars in the Milky Way's halo are ________.

What is the best evidence for an extremely massive black hole in the center of the Milky Way?

Observing our galaxy at radio wavelengths allows us to see through the dust in the disk that obscures our view.

Sound waves in the interstellar medium

Our Place in the Universe

Discovering the Universe for Yourself

The Science of Astronomy

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

Light: the Cosmic Messenger

Formation of Planetary Systems: Our Solar System and Beyond

Earth and the Terrestrial Worlds

Jovian Planet Systems

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

Our Star

Surveying the Stars

Star Stuff

Bizarre Stellar Graveyard

Galaxies and the Foundation of Modern Cosmology

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

The Beginning of Time

Life in the Universe

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Exam 14: Our Galaxy

About what percentage of the mass of a molecular cloud is in the form of dust?

Interstellar dust consists mostly of ________.

Most of the current star formation in the Milky Way occurs in its spiral arms.

Why do we believe that most of the mass of the Milky Way is in the form of dark matter?

What do we mean by the star-gas-star cycle?

How do we know the total mass of the Milky Way Galaxy that is contained within the Sun's orbital path?

Briefly describe the star-gas-star cycle.

What is the best evidence for a supermassive black hole in the center of the Milky Way Galaxy?

Harlow Shapley concluded that the Sun was not located at the center of the Milky Way Galaxy by

Which kind of star is highly unlikely to be found in the halo of the Milky Way?

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

Where does most star formation occur in the Milky Way Galaxy?

Suppose a scientist holds a press conference at which he claims that 10% of the matter in the Milky Way is in the form of dust grains. Does his claim seem reasonable? Why or why not?

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

What kind of object do we think lies in the center of the Milky Way Galaxy?

Most stars in the Milky Way's halo are ________.

What is the best evidence for an extremely massive black hole in the center of the Milky Way?

Observing our galaxy at radio wavelengths allows us to see through the dust in the disk that obscures our view.

Sound waves in the interstellar medium

Our Place in the Universe

Discovering the Universe for Yourself

The Science of Astronomy

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

Light: the Cosmic Messenger

Formation of Planetary Systems: Our Solar System and Beyond

Earth and the Terrestrial Worlds

Jovian Planet Systems

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

Our Star

Surveying the Stars

Star Stuff

Bizarre Stellar Graveyard

Galaxies and the Foundation of Modern Cosmology

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

The Beginning of Time

Life in the Universe

Filters