Until recently most astronomers believed that the space between the

Question

Until recently most astronomers believed that the space between the galaxies in our universe was a near-perfect vacuum. This  orthodox view of the universe  is now being challenged by astronomers who believe that a heavy “rain” of gas is falling into many galaxies from the supposedly empty space around them. The gas apparently condenses into a collection of small stars, each a little larger than the planet Jupiter. These stars vastly outnumber the other stars in a given galaxy. The amount of “intergalactic rainfall” into some of these galaxies has been enough to double their mass in the time since they formed. Scientists have begun to suspect that this intergalactic gas is probably a mixture of gases left over from the “big bang” when the galaxies were formed and gas was forced out of galaxies by supernova explosions.

It is well known that when gas is cooled at a constant pressure its volume decreases. Thus, the physicist Fabian reasoned that as intergalactic gas cools, the cooler gas shrinks inward toward the center of the galaxy. Meanwhile its place is taken by hotter intergalactic gas from farther out on the edge of the galaxy, which cools as it is compressed and flows into the galaxy. The net result is a continuous flow of gas, starting as hot gases in intergalactic space and ending as a drizzle of cool gas called a “cooling flow,” falling into the central galaxy.

A fairly heretical idea in the 1970’s, the cooling-flow theory gained support when Fabian observed a cluster of galaxies in the constellation Perseus and found the central galaxy, NGC 1275, to be a strange-looking object with irregular, thin strands of gas radiating from it. According to previous speculation, these strands were gases that had been blown out by an explosion in the galaxy. Fabian, however, disagreed. Because the strands of gas radiating from NGC 1275 are visible in optical photographs, Fabian suggested that such strands consisted not of gas blown out of the galaxy but of cooling flows of gas streaming inward. He noted that the wavelengths of the radiation emitted by a gas would changes as the gas cooled, so that as the gas flowed into the galaxy and became cooler, it would emit not x-rays, but visible light, like that which was captured in the photographs. Fabian’s hypothesis was supported by Canizares’ determination in 1982 that most of the gas in the Perseus cluster was at a temperature of 80 million degrees Kelvin, whereas the gas immediately surrounding NGC 1275 (the subject of the photographs) was at one-tenth this temperature.   1 
 1. The primary purpose of the passage is to

(A) illustrate a hypothesis about the origin of galaxies
(B) provide evidence to dispute an accepted theory about the evolution of galaxies
(C) summarize the state of and prospects for research in intergalactic astronomy
(D) report new data on the origins of intergalactic gas
(E) reconcile opposing views on the formation of intergalactic gas

2 
 2. The author uses the phrase “orthodox view of the universe” ( Highlighted ) to refer to the belief that

(A) the space between the galaxies is devoid of matter
(B) the space between galaxies is occupied by stars that cannot be detected by optical photographs
(C) galaxies have decreased in mass by half since their formation
(D) galaxies contain stars, each the size of Jupiter, which form clusters
(E) galaxies are being penetrated by gas forced out of other galaxies by supernova explosions

3 
 3. It can be inferred from the passage that, if Fabian is correct, gas in the peripheral regions of a galaxy cluster

(A) streams outward into intergalactic space
(B) is hotter than gas in the central regions of the galaxy
(C) is composed primarily of gas left over from the big bang
(D) results in the creation of unusually large stars
(E) expands to increase the size of the galaxy

4 
 4. The author of the passage probably mentions Canizares’ determination in order to

(A) clarify an ambiguity in Fabian’s research findings
(B) illustrate a generalization about the temperature of gas in a galaxy cluster
(C) introduce a new argument in support of the orthodox view of galaxies
(D) provide support for Fabian’s assertions about the Perseus galaxies
(E) provide an alternate point of view concerning the movement of gas within a galaxy cluster

5 
 5. According to the passage, Fabian believes that gas flowing into a central galaxy has which of the following characteristics?

(A) It is one-tenth hotter than it was in the outer regions of the galaxy cluster.
(B) It emits radiation with wavelengths that change as the gas moves toward the center of the galaxy.
(C) The total amount of radiation emitted diminishes as the gas cools.
(D) It loses 90 percent of its energy as it moves to the center of the galaxy.
(E) It condenses at a rate much slower than the rate of decrease in temperature as the gas flows inward.

6 
 6. According to the passage, Fabian’s theory makes use of which of the following principles?

(A) Gas emanating from an explosion will be hotter the more distant it is from the origin.
(B) The wavelength of radiation emitted by a gas as it cools remains constant.
(C) If pressure remains constant, the volume of a gas will decrease as it is cooled.
(D) The volume of a gas will increase as the pressure increases.
(E) As gas cools, its density decreases.

7 
 7. It can be inferred from the passage that which of the following is true of Fabian’s theory?

(A) It did not receive approval until Canizares’ work was published.
(B) It was not widely accepted in the 1970’s.
(C) It did not receive support initially because technology was not available to confirm its tenets.
(D) It supports earlier speculation that intergalactic gas was largely the result of explosions outside the galaxy.
(E) It was widely challenged until x-ray evidence of gas temperatures in NGC 1275 had been presented.

jaisonsunny77 · Accepted Answer

1. The primary purpose of the passage is to

(B) provide evidence to dispute an accepted theory about the evolution of galaxies

In the passage, it is mentioned that ".... This  orthodox view  of the universe is  now being challenged ...". The rest of the passage describes the new theory of 'heavy gas rain'. (B) highlights this perfectly. Hence,  (B) is the right answer choice.

2. The author uses the phrase “orthodox view of the universe” (Highlighted) to refer to the belief that

In the first line of this passage, it is mentioned that "...the  space between the galaxies  in our universe  was a near-perfect vacuum. " The official definition of vacuum is " space devoid of matter ".

this is what (A) says. Hence,  (A) is the right answer choice.

3. It can be inferred from the passage that, if Fabian is correct, gas in the peripheral regions of a galaxy cluster

To answer question 3, we need to have a good idea of what Fabian's theory is all about. So, let us summarize Fabian's theory first:

In paragraph 2, we have the following information on Fabian's theory "...a continuous flow of gas, starting as hot gases in intergalactic space and ending as a drizzle of cool gas called a “cooling flow"

In paragraph 3, we have "Fabian observed a cluster of galaxies..... NGC 1275...  such strands consisted  not of gas blown out of the galaxy but  of cooling flows of gas streaming inward.
 "

Combining this information, we get to infer that gas in the peripheral regions of a galaxy cluster is hotter than gas in the central regions of the galaxy

Therefore,  (B) is the correct answer choice.

4. The author of the passage probably mentions Canizares’ determination in order to

(D)  provide support for Fabian’s assertions about the Perseus galaxies

In the last paragraph, we have "Fabian’s hypothesis was supported by Canizares’ determination"

hence,  (D) is the right answer.

5. According to the passage, Fabian believes that gas flowing into a central galaxy has which of the following characteristics?

(B) It emits radiation with wavelengths that change as the gas moves toward the center of the galaxy.

In the last paragraph, we have ".....  the wavelengths of the radiation emitted by a gas would change as the gas cooled , so that as the gas flowed into the galaxy and became cooler....."

Hence,  (B) is the right answer.

6. According to the passage, Fabian’s theory makes use of which of the following principles?

(C) If pressure remains constant, the volume of a gas will decrease as it is cooled

In the second paragraph, we have "It is well known that when gas is cooled at a constant pressure its volume decreases. Thus, the physicist Fabian reasoned that...."

This is what (C) says. Hence,  (C) is the right answer choice .

7. It can be inferred from the passage that which of the following is true of Fabian’s theory?

(B) It was not widely accepted in the 1970’s.

In the first line of the last paragraph, we have 'A fairly  heretical  idea in the 1970’s, the cooling-flow theory gained support when Fabian observed a cluster...'

heretical means 'holding an opinion at odds with what is generally accepted.'

hence,  (B) is the correct answer choice.

avi12345 · Answer

1. The primary purpose of the passage is to

(B) provide evidence to dispute an accepted theory about the evolution of galaxies - Para 1 states the a theory already existed, but Fabian challenged old theory by suggesting a new theory. Para2 and 3 supports this new theory. Hence, overall, passage provides evidence to dispute an accepted theory about the evolution of galaxies ( New Theory)

(E) reconcile opposing views on the formation of intergalactic gas - The passage is not comparing both views. It introduces old theory, then expands on the new theory to dispute old theory.

avi12345 · Answer

I have already explained Question 1.

3. It can be inferred from the passage that, if Fabian is correct, gas in the peripheral regions of a galaxy cluster
(A) streams outward into intergalactic space
(B) is hotter than gas in the central regions of the galaxy
(C) is composed primarily of gas left over from the big bang
(D) results in the creation of unusually large stars
(E) expands to increase the size of the galaxy

From the second para "Thus, the physicist Fabian reasoned that as intergalactic gas cools, the cooler gas shrinks inward toward the center of the galaxy. Meanwhile its place is taken by hotter intergalactic gas from farther out on the edge of the galaxy, which cools as it is compressed and flows into the galaxy."

From above, it it clear that gas in the external region is hotter than the gas in the central region. As gas cools down, it moves towards inner side of the galaxy.

The best option that summarizes above point is : (B) is hotter than gas in the central regions of the galaxy

5. According to the passage, Fabian believes that gas flowing into a central galaxy has which of the following characteristics?
(A) It is one-tenth hotter than it was in the outer regions of the galaxy cluster.
(B) It emits radiation with wavelengths that change as the gas moves toward the center of the galaxy.
(C) The total amount of radiation emitted diminishes as the gas cools.
(D) It loses 90 percent of its energy as it moves to the center of the galaxy.
(E) It condenses at a rate much slower than the rate of decrease in temperature as the gas flows inward.

From the 3rd para , "Because the strands of gas radiating from NGC 1275 are visible in optical photographs, Fabian suggested that such strands consisted not of gas blown out of the galaxy but of cooling flows of gas streaming inward. He noted that the wavelengths of the radiation emitted by a gas would changes as the gas cooled, so that as the gas flowed into the galaxy and became cooler, it would emit not x-rays, but visible light, like that which was captured in the photographs"

The lines above state that as gas cools down and moves towards the inner side of galaxy, the wavelength of the radiation would change

The option that summarizes above is : (B) It emits radiation with wavelengths that change as the gas moves toward the center of the galaxy.

Cheers

!

Radheya · Answer

Can someone throw some light on why option B of Q7 is correct and not option D?

Thanks

vivek360 · Answer

Let me try:
Option D is opposite of what is mentioned in the passage: From paragraph 1—"Scientists have begun to suspect that this intergalactic gas is probably a mixture of gases left over from the “big bang” when the galaxies were formed and gas was forced out of galaxies by supernova explosions." So we can infer that intergalactic gas was a result not of explosions  outside  the galaxies, but rather of explosions within them.

Option B is correct because from last paragraph we have—"A fairly heretical idea in the 1970’s, the cooling-flow theory gained support when Fabian observed a cluster of galaxies in the constellation Perseus ...". So we can infer that because the idea was  heretical , it was not widely accepted at that time.

anchopra · Answer

This is regarding Question 1:
I crossed out option B as there is no talk about "evolution of galaxies", rather, "what is filled between the galaxies". Please help me understand how to come to the conclusion that these theories are about "evolution of galaxies". How can anyone explain the evolution of galaxies by reading this comprehension?

sabstas · Answer

Hi anchopra, this is my first time replying to someone on here, so bear with me as I try to explain as best as possible

From the first paragraph, we learn that the passage will be talking about a hypothesis that counteracts a traditional belief. This traditional belief being that there is no matter between galaxies. There's some helpful parts in the first paragraph that talk about evolution: "heavy “rain” of gas is falling into many galaxies... gas condenses into a collection of small stars, each a little larger than the planet Jupiter" - From this section we see that this "rain" is creating stars which are creating galaxies. The present tense also helps show that this is something that is currently occurring. "The amount of “intergalactic rainfall” into some of these galaxies has been enough to double their mass in the time since they formed... mixture of gases left over from the “big bang” when the galaxies were formed." - From reading this section, it can be seen that the author is talking about the continual creation of these galaxies ("since they formed"). You are correct that the passage talks about what is filled between the galaxies, but the passage does refer to the continual creation of stars/galaxies (space is constantly moving and changing even to this day!). When looking at answer B) I also was a little unsure about the "evolution of galaxies" part, but I think the most important statement from option B) is the "provide evidence to dispute an accepted theory" part. Hope this helps a bit!

ducchi1301 · Answer

1. The primary purpose of the passage is to

(A) illustrate a hypothesis about the origin of galaxies  (POE, it's not about the origin of galaxies, but discuss information about the structure of gap between galaxies.)  
  (B) provide evidence to dispute an accepted theory about the evolution of galaxies   (This is correct, as provided:    "Until recently most astronomers believed that the space between the galaxies in our universe was a near-perfect vacuum. This  orthodox view of the universe  is now being challenged by astronomers who believe that...") 
 (C) summarize the state of and prospects for research in intergalactic astronomy  (POE, because no possibilities for research is provided in the text.)  
 (D) report new data on the origins of intergalactic gas.  (It's not compelling, to be honest.)

7. It can be inferred from the passage that which of the following is true of Fabian’s theory?

(A) It did not receive approval until Canizares’ work was published.    (There's no evidence to support this idea.)  
  (B)     It was not widely accepted in the 1970’s.   (The first sentence in the last paragraph shows that Fabian's theory is heretical, which is equivalent to not compelling. Therefore, B is correct.)  
 (C) It did not receive support initially because technology was not available to confirm its tenets.  (There's no evidence in the passage.)  
 (D) It supports earlier speculation that intergalactic gas was largely the result of explosions outside the galaxy.  (It's contradictory to the idea expressed.)  
 (E) It was widely challenged until x-ray evidence of gas temperatures in NGC 1275 had been presented.  (AS above.)

5. According to the passage, Fabian believes that gas flowing into a central galaxy has which of the following characteristics?

(A) It is one-tenth hotter than it was in the outer regions of the galaxy cluster.  (POE)  
  (B) It emits radiation with wavelengths that change as the gas moves toward the center of the galaxy. (He noted that the wavelengths of the radiation emitted by a gas would changes as the gas cooled")  
 (C) The total amount of radiation emitted diminishes as the gas cools.  (POE)  
 (D) It loses 90 percent of its energy as it moves to the center of the galaxy.  (This idea is from Canizares, not Fabian. Therefore, don't misinterpret it.)  
 (E) It condenses at a rate much slower than the rate of decrease in temperature as the gas flows inward.  (POE)

VerbalBot · Answer

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