Question 1

The ________ of light passing through thin dust clouds lets us map the Galaxy's magneticfield.

Accepted Answer

A)  diffraction
B)  granulation
C)  ionization
D)  polarization
E)  absorptionF) A) and B)
G) C) and E)

Question 2

Dust particles and magnetic fields in the interstellar medium are revealed by ________ oflight.

Accepted Answer

The answer of Dust particles and magnetic fields in the...

Question 3

How does emission of long wavelength radio radiation from neutral hydrogen help usovercome the shortcomings of visible light in mapping out distant parts of our galaxy?

Accepted Answer

It allows us to detect interst...

Question 4

Neutral hydrogen is most obvious in the electromagnetic spectrum:

Accepted Answer

A)  in yellow light of the Sun's continuum.
B)  at 656.3 nm, hydrogen alpha red.
C)  at 21 cm in the radio region.
D)  at 121.3 nm, the Lyman alpha ultraviolet line.
E)  Neutral hydrogen has yet to be detected in space.F) B) and D)
G) B) and C)

Question 5

Reflection nebulae usually appear red.

Accepted Answer

A) True 
 B)False

Question 6

Molecular hydrogen is not very useful for mapping molecular clouds because:

Accepted Answer

A)  molecular hydrogen does not occur in most molecular clouds.
B)  molecular hydrogen puts out radiation similar to most stars.
C)  molecular hydrogen and atomic hydrogen cannot be distinguished in telescopes.
D)  radiation from carbon monoxide overwhelms radiation from molecular hydrogen.
E)  molecular hydrogen is essentially invisible in the radio portion of the spectrum.F) A) and B)
G) C) and E)

Question 7

What are the very cold (about 20 K) , dense clouds of gas thought to be the most massiveobjects in the Galaxy called?

Accepted Answer

A)  emission nebulae
B)  absorption clouds
C)  dust clouds
D)  molecular clouds
E)  reflection nebulaeF) A) and E)
G) B) and E)

Question 8

Interstellar reddening of starlight occurs because the interstellar dust preferentially ________the blue light.

Accepted Answer

The answer of Interstellar reddening of starlight occurs because the...

Question 9

The temperature inside an H II region is colder than inside an H I region.

Accepted Answer

A) True 
 B)False

Question 10

Why can radio waves get through the dust clouds, but light is blocked?

Accepted Answer

The interstellar dust grains a...

Question 11

Explain how "forbidden" lines appear in spectra of emission nebulae.

Accepted Answer

These lines correspond to excited states...

Question 12

How is 21 cm radiation produced?

Accepted Answer

When the electron orbiting the...

Question 13

Molecular hydrogen can best be detected by ultraviolet observations.

Accepted Answer

A) True 
 B)False

Question 14

Why does a reflection nebula look blue?

Accepted Answer

The nebula is illuminated by t...

Question 15

Emission nebulae are blue.

Accepted Answer

A) True 
 B)False

Question 16

What feature of interstellar dust is inferred by the polarization of starlight?

Accepted Answer

A)  its shape
B)  its composition
C)  its location in space
D)  its presence in molecular clouds
E)  its presence in dark nebulaeF) C) and E)
G) A) and C)

Question 17

In the Milky Way Galaxy, gas and dust are found:

Accepted Answer

A)  in molecular clouds.
B)  everywhere.
C)  in neutral hydrogen clouds.
D)  in dark nebulae.
E)  in emission nebulae.F) B) and C)
G) A) and B)

Question 18

Explain why interstellar molecules are best observed at radio wavelengths.

Accepted Answer

Interstellar molecules are best observed...

Question 19

Astronomers use roman numerals to indicate the ionization state of a gas. Ionized hydrogenis indicated by which of the following symbols?

Accepted Answer

A)  H II
B)    H2\mathrm { H } _ { 2 }H2​ 
C)  H I
D)    H11\mathrm { H } _ { 1 } ^ { 1 }H11​ 
E)  H III F) B) and D)
G) A) and D)

Question 20

The form of electromagnetic radiation least blocked by a dark nebula is ________.

Accepted Answer

The answer of The form of electromagnetic radiation least blocked...

Exam 18: The Interstellar Medium: Gas and Dust Among the Stars

Why can radio waves get through the dust clouds, but light is blocked?

Correct AnswerverifiedThe interstellar dust grains a...View AnswerShow Answer

What feature of interstellar dust is inferred by the polarization of starlight?

Correct AnswerverifiedShow Answer

In the Milky Way Galaxy, gas and dust are found:

Correct AnswerverifiedShow Answer

Why does a reflection nebula look blue?

Correct AnswerverifiedThe nebula is illuminated by t...View AnswerShow Answer

What are the very cold (about 20 K) , dense clouds of gas thought to be the most massiveobjects in the Galaxy called?

Correct AnswerverifiedShow Answer

The form of electromagnetic radiation least blocked by a dark nebula is ________.

Correct AnswerverifiedShow Answer

Astronomers use roman numerals to indicate the ionization state of a gas. Ionized hydrogenis indicated by which of the following symbols?

Correct AnswerverifiedShow Answer

Emission nebulae are blue.

Correct AnswerverifiedShow Answer

How does emission of long wavelength radio radiation from neutral hydrogen help usovercome the shortcomings of visible light in mapping out distant parts of our galaxy?

Correct AnswerverifiedIt allows us to detect interst...View AnswerShow Answer

Neutral hydrogen is most obvious in the electromagnetic spectrum:

Correct AnswerverifiedShow Answer

Dust particles and magnetic fields in the interstellar medium are revealed by ________ oflight.

Correct AnswerverifiedShow Answer

Explain how "forbidden" lines appear in spectra of emission nebulae.

Correct AnswerverifiedThese lines correspond to excited states...View AnswerShow Answer

Molecular hydrogen can best be detected by ultraviolet observations.

Correct AnswerverifiedShow Answer

Reflection nebulae usually appear red.

Correct AnswerverifiedShow Answer

Explain why interstellar molecules are best observed at radio wavelengths.

Correct AnswerverifiedInterstellar molecules are best observed...View AnswerShow Answer

Interstellar reddening of starlight occurs because the interstellar dust preferentially ________the blue light.

Correct AnswerverifiedShow Answer

How is 21 cm radiation produced?

Correct AnswerverifiedWhen the electron orbiting the...View AnswerShow Answer

The ________ of light passing through thin dust clouds lets us map the Galaxy's magneticfield.

Correct AnswerverifiedShow Answer

The temperature inside an H II region is colder than inside an H I region.

Correct AnswerverifiedShow Answer

Molecular hydrogen is not very useful for mapping molecular clouds because:

Correct AnswerverifiedShow Answer

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The interstellar dust grains a...
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The nebula is illuminated by t...
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It allows us to detect interst...
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These lines correspond to excited states...
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Interstellar molecules are best observed...
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When the electron orbiting the...
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