Question 1

What are cosmic rays?

Accepted Answer

A)  Subatomic particles that travel close the speed of light 
B)  Another name for gamma rays and X-rays 
C)  Fast moving dust particles in the interstellar medium 
D)  The highest-energy form of light 
E)  Lasers used as weapons by extraterrestrials 
A)  Subatomic particles that travel close the speed of light 
B)  Another name for gamma rays and X-rays 
C)  Fast moving dust particles in the interstellar medium 
D)  The highest-energy form of light 
E)  Lasers used as weapons by extraterrestrials A

Question 2

If you were to take a voyage through the entire disk of the Milky Way, what kind of material would you spend most of your time in?

Accepted Answer

A)  empty space-a pure vacuum 
B)  hot bubbles of ionized hydrogen 
C)  star clusters 
D)  rarefied clouds of atomic hydrogen 
E)  cool, dense clouds of molecular hydrogen 
A)  empty space-a pure vacuum 
B)  hot bubbles of ionized hydrogen 
C)  star clusters 
D)  rarefied clouds of atomic hydrogen 
E)  cool, dense clouds of molecular hydrogen D

Question 3

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

Accepted Answer

A) True 
 B)False  True

Question 4

The image of our galaxy in radio emission from carbon monoxide maps the distribution of molecular clouds. Which of the following would give a similar picture of our galaxy?

Accepted Answer

A)  21-cm-line radio emission from atomic hydrogen. 
B)  visible light, showing the edges of supernova bubbles. 
C)  visible light, which is closest to how the night sky appears from Earth. 
D)  X-rays from hot gas bubbles in the disk. 
E)  infrared emission from interstellar dust grains. 
A)  21-cm-line radio emission from atomic hydrogen. 
B)  visible light, showing the edges of supernova bubbles. 
C)  visible light, which is closest to how the night sky appears from Earth. 
D)  X-rays from hot gas bubbles in the disk. 
E)  infrared emission from interstellar dust grains.

Question 5

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

Accepted Answer

Both arise for the same physical reason:

Question 6

Most nearby stars move relative to the Sun at speeds below about 30 km/s. Suppose you observe a nearby star that is moving much faster than this (say, 300 km/s). Which of the following is a likely explanation for its high speed?

Accepted Answer

A)  It is probably a halo star that is currently passing through the disk. 
B)  It is a very young star, recently formed. 
C)  It has been pushed to high speed by the shock wave from a nearby supernova. 
D)  It is a very high mass star. 
A)  It is probably a halo star that is currently passing through the disk. 
B)  It is a very young star, recently formed. 
C)  It has been pushed to high speed by the shock wave from a nearby supernova. 
D)  It is a very high mass star.

Question 7

Approximately how far is the Sun from the center of the galaxy?

Accepted Answer

A)  28 light-years 
B)  280 light-years 
C)  2,800 light-years 
D)  28,000 light-years 
E)  28 million light-years 
A)  28 light-years 
B)  280 light-years 
C)  2,800 light-years 
D)  28,000 light-years 
E)  28 million light-years

Question 8

What is Sgr A∗?

Accepted Answer

A)  a source of bright X-ray emission coming from the entire constellation of Sagittarius 
B)  a source of bright radio emission in the center of our galaxy 
C)  a source of bright ultraviolet light near the center of our galaxy 
D)  the brightest star in the constellation Sagittarius 
E)  the bulge at the center of our galaxy 
A)  a source of bright X-ray emission coming from the entire constellation of Sagittarius 
B)  a source of bright radio emission in the center of our galaxy 
C)  a source of bright ultraviolet light near the center of our galaxy 
D)  the brightest star in the constellation Sagittarius 
E)  the bulge at the center of our galaxy

Question 9

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

Question 10

Which of the following statements is not true of the object known as Sgr A* in the center of our Galaxy?

Accepted Answer

A)  It is by far the brightest source of visible light lying in the direction of the galactic center. 
B)  It is thought to harbor a black hole of more than 3 million solar masses. 
C)  It is a source of X-ray emission that we have observed with telescopes in space. 
D)  It is a source of bright radio emission. 
A)  It is by far the brightest source of visible light lying in the direction of the galactic center. 
B)  It is thought to harbor a black hole of more than 3 million solar masses. 
C)  It is a source of X-ray emission that we have observed with telescopes in space. 
D)  It is a source of bright radio emission.

Question 11

Which of the following observations confirms that Sgr A at the center of our galaxy is indeed a supermassive black hole?

Accepted Answer

A)  Measurements of occasional X-ray emission from Sgr A 
B)  Measurements of trans-dimensional space warps in the vicinity of Sgr A 
C)  Measurements of radio emission from gas around Sgr A 
D)  Measurements of the orbits of stars around Sgr A 
A)  Measurements of occasional X-ray emission from Sgr A 
B)  Measurements of trans-dimensional space warps in the vicinity of Sgr A 
C)  Measurements of radio emission from gas around Sgr A 
D)  Measurements of the orbits of stars around Sgr A

Question 12

The most common form of gas in the disk of the Milky Way galaxy is ________.

Accepted Answer

A)  atomic hydrogen gas 
B)  molecular hydrogen 
C)  gas in hot bubbles 
D)  gas in stellar winds 
A)  atomic hydrogen gas 
B)  molecular hydrogen 
C)  gas in hot bubbles 
D)  gas in stellar winds

Question 13

Which star is older?

Accepted Answer

A)  An A star in the globular cluster M13 
B)  Both stars (the A and M star) are the same age. 
C)  An M star in the globular cluster M13 
A)  An A star in the globular cluster M13 
B)  Both stars (the A and M star) are the same age. 
C)  An M star in the globular cluster M13

Question 14

How does the diameter of the disk of Milky Way Galaxy compare to its thickness?

Accepted Answer

A)  The diameter is about 100 times as great as the thickness. 
B)  The diameter and thickness are roughly equal. 
C)  The diameter is about 10 times as great as the thickness. 
D)  The diameter is about 100,000 times as great as the thickness. 
A)  The diameter is about 100 times as great as the thickness. 
B)  The diameter and thickness are roughly equal. 
C)  The diameter is about 10 times as great as the thickness. 
D)  The diameter is about 100,000 times as great as the thickness.

Question 15

The galactic center lies in the direction of which constellation?

Accepted Answer

A)  Orion 
B)  the Big Dipper 
C)  Leo 
D)  Sagittarius 
E)  Taurus 
A)  Orion 
B)  the Big Dipper 
C)  Leo 
D)  Sagittarius 
E)  Taurus

Question 16

What do we mean by a protogalactic cloud?

Accepted Answer

A)  A cloud of hydrogen and helium that contracts to become a galaxy 
B)  A term once used historically to refer to any galaxy 
C)  The cloud-like halo that surrounds the disks of spiral galaxies 
D)  A cloud of gas that was once a galaxy 
A)  A cloud of hydrogen and helium that contracts to become a galaxy 
B)  A term once used historically to refer to any galaxy 
C)  The cloud-like halo that surrounds the disks of spiral galaxies 
D)  A cloud of gas that was once a galaxy

Question 17

What is an ionization nebula?

Accepted Answer

A)  A region of very hot, low-density gas surrounding a recent supernova 
B)  A clump of gas that will soon give birth to a new star 
C)  A colorful cloud of gas that glows because it is heated by light from nearby hot stars 
D)  A name sometimes used to describe spiral galaxies besides the Milky Way 
A)  A region of very hot, low-density gas surrounding a recent supernova 
B)  A clump of gas that will soon give birth to a new star 
C)  A colorful cloud of gas that glows because it is heated by light from nearby hot stars 
D)  A name sometimes used to describe spiral galaxies besides the Milky Way

Question 18

How do disk stars orbit the center of the galaxy?

Accepted Answer

A)  They all orbit in roughly the same plane and in the same direction. 
B)  They have orbits randomly inclined and in different directions relative to the galactic center. 
C)  They follow spiral paths along the spiral arms. 
D)  They follow orbits that move up and down through the disk, typically taking them about 50,000 light-years above and below the disk on each orbit. 
A)  They all orbit in roughly the same plane and in the same direction. 
B)  They have orbits randomly inclined and in different directions relative to the galactic center. 
C)  They follow spiral paths along the spiral arms. 
D)  They follow orbits that move up and down through the disk, typically taking them about 50,000 light-years above and below the disk on each orbit.

Question 19

Which of the following molecules is the most abundant in molecular clouds?

Accepted Answer

A)  H₂ 
B)  CO 
C)  H₂O 
D)  NH₃ 
A)  H₂ 
B)  CO 
C)  H₂O 
D)  NH₃

Question 20

Observational Bias: The history of human understanding of the structure of the Milky Way starts with the bias that humans use visible light to see. Imagine you were a creature on another planet in the disk of the Milky Way who used radio waves to "see" the universe. What would have been your starting point for the structure of the Milky Way? What components would you have found easier to detect? What components would have been harder?

Accepted Answer

As a creature on another planet in the d

What are cosmic rays?

If you were to take a voyage through the entire disk of the Milky Way, what kind of material would you spend most of your time in?

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

The image of our galaxy in radio emission from carbon monoxide maps the distribution of molecular clouds. Which of the following would give a similar picture of our galaxy?

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

Most nearby stars move relative to the Sun at speeds below about 30 km/s. Suppose you observe a nearby star that is moving much faster than this (say, 300 km/s). Which of the following is a likely explanation for its high speed?

Approximately how far is the Sun from the center of the galaxy?

What is Sgr A∗?

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?

Which of the following statements is not true of the object known as Sgr A* in the center of our Galaxy?

Which of the following observations confirms that Sgr A at the center of our galaxy is indeed a supermassive black hole?

The most common form of gas in the disk of the Milky Way galaxy is ________.

Which star is older?

How does the diameter of the disk of Milky Way Galaxy compare to its thickness?

The galactic center lies in the direction of which constellation?

What do we mean by a protogalactic cloud?

What is an ionization nebula?

How do disk stars orbit the center of the galaxy?

Which of the following molecules is the most abundant in molecular clouds?

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

Exam 14: Our Galaxy

What are cosmic rays?

If you were to take a voyage through the entire disk of the Milky Way, what kind of material would you spend most of your time in?

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

The image of our galaxy in radio emission from carbon monoxide maps the distribution of molecular clouds. Which of the following would give a similar picture of our galaxy?

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

Most nearby stars move relative to the Sun at speeds below about 30 km/s. Suppose you observe a nearby star that is moving much faster than this (say, 300 km/s). Which of the following is a likely explanation for its high speed?

Approximately how far is the Sun from the center of the galaxy?

What is Sgr A∗?

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?

Which of the following statements is not true of the object known as Sgr A* in the center of our Galaxy?

Which of the following observations confirms that Sgr A at the center of our galaxy is indeed a supermassive black hole?

The most common form of gas in the disk of the Milky Way galaxy is ________.

Which star is older?

How does the diameter of the disk of Milky Way Galaxy compare to its thickness?

The galactic center lies in the direction of which constellation?

What do we mean by a protogalactic cloud?

What is an ionization nebula?

How do disk stars orbit the center of the galaxy?

Which of the following molecules is the most abundant in molecular clouds?

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