The dark regions in the starry night sky are not pockets in the

Question

The dark regions in the starry night sky are not pockets in the universe that are devoid of stars as had long been thought. Rather, they are dark because of interstellar dust that hides the stars behind it. Although its visual effect is so pronounced, dust is only a minor constituent of the material, extremely low in density, that lies between the stars. Dust accounts for about one percent of the total mass of interstellar matter. The rest is hydrogen and helium gas, with small amounts of other elements. The interstellar material, rather like terrestrial clouds, comes in all shapes and sizes. The average density of interstellar material in the vicinity of our Sun is 1,000 to 10,000 times less than the best terrestrial laboratory vacuum. It is only because of the enormous interstellar distances that so little material per unit of volume becomes so significant. Optical astronomy is most directly affected, for although interstellar gas is perfectly transparent, the dust is not.   1 
 1. According to the passage, which of the following is a direct perceptual consequence of interstellar dust?

(A) Some stars are rendered invisible to observers on Earth. 
(B) Many visible stars are made to seem brighter than they really are. 
(C) The presence of hydrogen and helium gas is revealed. 
(D) The night sky appears dusty at all times to observers on Earth. 
(E) The dust is conspicuously visible against a background of bright stars.

2 
 2. It can be inferred from the passage that the density of interstellar material is

(A) higher where distances between the stars are shorter 
(B) equal to that of interstellar dust 
(C) unusually low in the vicinity of our Sun 
(D) independent of the incidence of gaseous components 
(E) not homogeneous throughout interstellar space

3 
 3. It can be inferred from the passage that it is because space is so vast that

(A) little of the interstellar material in it seems substantial 
(B) normal units of volume seem futile for measurements of density 
(C) stars can be far enough from Earth to be obscured even by very sparsely distributed matter 
(D) interstellar gases can, for all practical purposes, be regarded as transparent 
(E) optical astronomy would be of little use even if no interstellar dust existed

Skywalker18 · Accepted Answer

All correct in 3 mins 45 seconds, including 1 min 45 seconds to read.

1. According to the passage, which of the following is a direct perceptual consequence of interstellar dust?

(A) Some stars are rendered invisible to observers on Earth. - Correct
The dark regions in the starry night sky are not pockets in the universe that are devoid of stars as had long been thought. Rather, they are dark because of interstellar dust that hides the stars behind it.

2. It can be inferred from the passage that the density of interstellar material is 
(E) not homogeneous throughout interstellar space - Correct
The average density of interstellar material in the vicinity of our Sun is 1,000 to 10,000 times less than the best terrestrial laboratory vacuum. --> since the passage talks about average density, we can infer that the density is not homogeneous

3. It can be inferred from the passage that it is because space is so vast that 
(C) stars can be far enough from Earth to be obscured even by very sparsely distributed matter - Correct
It is only because of the enormous interstellar distances that so little material per unit of volume becomes so significant. Optical astronomy is most directly affected, for although interstellar gas is perfectly transparent, the dust is not.

greenisthecolor · Answer

Could someone tell me what is wrong in option A?

I chose A as it resembled the 2nd last sentence in the passage.

Carcass · Answer

It is only because of the enormous interstellar  distances that so little material per unit  of volume becomes so  significant.

(C) stars can be   far enough   from Earth to be obscured even by very  sparsely  distributed matter

What is sparsely, which means NOT so dense, to a long-distance the become significant in obscuring the stars

(A) little of the interstellar material in it   seems substantial

It is not the same paraphrasing. Moreover, in C we talk about the matter + other material = Interstellar Material.

In A , on the other hand, we care about ONLY of matter

Hope is now more clear to you. The passage is short but nasty

Regards

GMATStudyStudent · Answer

Supporting details for Option C:

1. The dark regions in the starry night sky are not pockets in the universe that are devoid of stars as had long been thought. Rather, they are dark because of interstellar dust that hides the stars behind it.
2. Dust accounts for about one percent of the total mass of interstellar matter.

Option A is incorrect because despite the avg. low density of interstellar material, interstellar material has a substantial effect as it can hide the stars behind it.

Spunk17 · Answer

Can someone explain the second question? Why is C wrong and how do I interpret that density is not homogenous throughout interstellar space. (From which part of the passage I should be deriving this inference)

2. It can be inferred from the passage that the density of interstellar material is

(A) higher where distances between the stars are shorter
(B) equal to that of interstellar dust
(C) unusually low in the vicinity of our Sun
(D) independent of the incidence of gaseous components
(E) not homogeneous throughout interstellar space

bM22 · Answer

Hi  Spunk17 ,

E can be inferred from the lines: "The average density of interstellar material in the vicinity of our Sun is 1,000 to 10,000 times less than the best terrestrial laboratory vacuum. Average density implies that density is not homogeneous.
Same lines tell us that C is incorrect, as the option talks about the density, and what's mentioned in the passage is average density. Also, the average density in the of interstellar material in the vicinity of the Sun is less when compared to the best terrestrial laboratory vacuum. But what is option C based on? We cannot infer with certainty that the density would be "unusually low" in the vicinity of our Sun.

Hope This Helps.
Thanks.

TheAdmissionHub · Answer

What the author does:
The author explains why some regions of the night sky appear dark and describes the role of interstellar dust and gas.
 
Brief summary:
Dark regions of the sky are not empty; they appear dark because interstellar dust blocks the light from stars. Dust makes up only about 1% of interstellar matter, while most of it is hydrogen and helium gas.
 1. According to the passage, which of the following is a direct perceptual consequence of interstellar dust? 
 
 (A) Some stars are rendered invisible to observers on Earth.
  Correct:   The passage says that interstellar dust  “hides the stars behind it.”  Therefore, some stars cannot be seen by observers on Earth.
 (B) Many visible stars are made to seem brighter than they really are.
 Wrong:  The passage says the opposite: dust  blocks  starlight rather than making stars appear brighter.
 (C) The presence of hydrogen and helium gas is revealed.
 Wrong:  Hydrogen and helium gas are part of interstellar matter, but the passage does not say that dust directly reveals their presence
 (D) The night sky appears dusty at all times to observers on Earth.
 Wrong:  The passage does not say that the sky appears dusty. The dust itself is not necessarily visible; its effect is that it  blocks the light of stars .
 (E) The dust is conspicuously visible against a background of bright stars.
 Wrong:  The passage says that dust is  not transparent , but it does not say that the dust itself is conspicuously visible against bright stars.
 
 2. It can be inferred from the passage that the density of interstellar material is

(A) The density is higher where distances between the stars are shorter.
 WRONG:  The passage does not say that the density of interstellar material depends on the distance between stars.
(B) The density is equal to that of interstellar dust.
 WRONG:  Dust accounts for only about 1% of interstellar matter. Most of it is hydrogen and helium gas, so the passage does not suggest that their densities are equal.
(C) The density is unusually low in the vicinity of our Sun.
 WRONG:  The passage says that the density near the Sun is extremely low, but it does not compare it with the density in other regions enough to call it “unusually” low.
(D) The density is independent of the incidence of gaseous components.
 WRONG:  Most interstellar matter consists of hydrogen and helium gas, so gaseous components are an important part of interstellar material.
(E) The density is not homogeneous throughout interstellar space.
 CORRECT:  The passage says that interstellar material comes in all shapes and sizes, suggesting that it is not distributed uniformly throughout space.

3. It can be inferred from the passage that it is because space is so vast that 
 
(A) Little of the interstellar material in it seems substantial.
 WRONG:  The passage says that because of the enormous distances, a small amount of material per unit of volume can become significant. So it does not say that the material seems insubstantial.
(B) Normal units of volume seem futile for measurements of density.
 WRONG:  The passage does not say that normal units of volume are useless. It simply explains that interstellar material has a very low density.
(C) Stars can be far enough from Earth to be obscured even by very sparsely distributed matter.
 CORRECT : The passage explains that the interstellar material is extremely low in density, but because the distances between stars are enormous, even a small amount of dust can block the light of distant stars.
(D) Interstellar gases can, for all practical purposes, be regarded as transparent.
 WRONG:  The passage says that interstellar gas is perfectly transparent, but this is not because space is vast. It is a property of the gas itself
(E) Optical astronomy would be of little use even if no interstellar dust existed.
 WRONG:  The passage says that dust affects optical astronomy because it blocks light. Without dust, optical astronomy would actually be less affected.

The dark regions in the starry night sky are not pockets in the

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The dark regions in the starry night sky are not pockets in the

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615 to 715 in 15 Days (Ria's Strategies)

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