Question 1

Which of these is NOT a consequence of dust in the interstellar medium?

Accepted Answer

A)   reddening of stars' light that passes through the dust
B)   blue reflection nebulae around the Pleiades
C)   red light from the emission nebulae
D)   the dark nebulae that block 90% of the Milky Way from us visually
E)   terrestrial planets like our own

Question 2

The polarization of light passing though the dust grains shows that:

Accepted Answer

A)   the dust grains are elongated in shape.
B)   the dust grains are aligned by a weak interstellar magnetic field.
C)   the dust grains are chiefly made of iron.
D)   Both A and B are correct.
E)   All of the above are correct.

Question 3

The gas density in an emission nebula is typically about how many particles per cc?

Accepted Answer

A)   dozen
B)   hundred
C)   thousand
D)   hundred thousand
E)   million

Question 4

The gas in the interstellar medium consists of mostly heavy elements.

Accepted Answer

A) True 
 B)False

Question 5

Contrast the chemical composition of interstellar gas with that of interstellar dust.

Accepted Answer

Gas is almost all hydrogen and...

Question 6

The most common molecule in a molecular cloud is:

Accepted Answer

A)   methane, CH₄.
B)   molecular hydrogen, H₂.
C)   carbon monoxide, CO.
D)   water, H₂O.
E)   ammonia, NH₃.

Question 7

Emission nebulae are blue.

Accepted Answer

A) True 
 B)False

Question 8

The "Local Bubble" is:

Accepted Answer

A)   created by our Sun's solar wind, and extends well past Pluto's orbit.
B)   created by the bipolar jets of the young Sun, perpendicular to the ecliptic.
C)   about 100 pcs. across and transparent to extreme ultraviolet radiation.
D)   the region around the Milky Way where we can trace out its magnetic field.
E)   the cluster of galaxies our Milky Way and M-31 in Andromeda belong to.

Question 9

A reflection nebula is caused by:

Accepted Answer

A)   starlight reflected off of a surface.
B)   sunlight reflected off of a surface.
C)   sunlight scattered by dust particles.
D)   starlight scattered by dust particles.
E)   emission by ionized gas.

Question 10

Explain the colors of emission nebulae.

Accepted Answer

The predominant bright red is the emissi...

Question 11

Due to absorption of shorter wavelengths by interstellar dust clouds,distant stars appear:

Accepted Answer

A)   bluer.
B)   brighter.
C)   redder.
D)   larger.
E)   to have a higher radial velocity.

Question 12

Most molecules found in the giant molecular clouds are based on silicon.

Accepted Answer

A) True 
 B)False

Question 13

There is as much mass in the voids between the stars as in the stars themselves.

Accepted Answer

A) True 
 B)False

Question 14

What does the polarization of starlight tell us about the dust grains and the Galaxy?

Accepted Answer

The Galaxy's magnetic field al...

Question 15

Interstellar gas is composed of:

Accepted Answer

A)   only hydrogen.
B)   90% hydrogen, 9% helium by weight.
C)   10% hydrogen, 90% helium by numbers of atoms.
D)   some hydrogen, but mainly carbon dioxide.
E)   ammonia, methane, and water vapor.

Question 16

Spectra of stars often show narrow absorption lines from interstellar matter.What type of interstellar matter produces these?

Accepted Answer

A)   dust
B)   neutral gas
C)   ionized gas
D)   molecules
E)   All of the above.

Question 17

Why does a reflection nebula look blue?

Accepted Answer

The nebula is illuminated by t...

Question 18

Most interstellar clouds are:

Accepted Answer

A)   much bigger than our solar system.
B)   about the size of Earth.
C)   similar in size to clouds in Earth's atmosphere.
D)   much smaller than the clouds in Earth's atmosphere.
E)   about the size of a wavelength of light.

Question 19

Which of the following has NOT yet been observed in space?

Accepted Answer

A)   formaldehyde
B)   methyl alcohol
C)   DNA
D)   ammonia
E)   hydrogen cyanide

Question 20

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

Accepted Answer

A)   diffraction
B)   granulation
C)   ionization
D)   polarization
E)   absorption

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

Interstellar gas is composed of:

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The most common molecule in a molecular cloud is:

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Due to absorption of shorter wavelengths by interstellar dust clouds,distant stars appear:

Correct AnswerverifiedShow Answer

The polarization of light passing though the dust grains shows that:

Correct AnswerverifiedShow Answer

The gas density in an emission nebula is typically about how many particles per cc?

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Which of the following has NOT yet been observed in space?

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Emission nebulae are blue.

Correct AnswerverifiedShow Answer

The "Local Bubble" is:

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Why does a reflection nebula look blue?

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

The gas in the interstellar medium consists of mostly heavy elements.

Correct AnswerverifiedShow Answer

Spectra of stars often show narrow absorption lines from interstellar matter.What type of interstellar matter produces these?

Correct AnswerverifiedShow Answer

Most molecules found in the giant molecular clouds are based on silicon.

Correct AnswerverifiedShow Answer

Contrast the chemical composition of interstellar gas with that of interstellar dust.

Correct AnswerverifiedGas is almost all hydrogen and...View AnswerShow Answer

Most interstellar clouds are:

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What does the polarization of starlight tell us about the dust grains and the Galaxy?

Correct AnswerverifiedThe Galaxy's magnetic field al...View AnswerShow Answer

Which of these is NOT a consequence of dust in the interstellar medium?

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A reflection nebula is caused by:

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

Correct AnswerverifiedShow Answer

Explain the colors of emission nebulae.

Correct AnswerverifiedThe predominant bright red is the emissi...View AnswerShow Answer

There is as much mass in the voids between the stars as in the stars themselves.

Correct AnswerverifiedShow Answer

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The nebula is illuminated by t...
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Gas is almost all hydrogen and...
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The Galaxy's magnetic field al...
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The predominant bright red is the emissi...
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