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31 May 2023, 11:57
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Which of the following, if true, would most clearly undermine the possible explanation for the whirling gas in M87 that is mentioned in the last sentence of the first paragraph?
For this why is not option C the correct choice and why option B is correvt can someone assist
For this why is not option C the correct choice and why option B is correvt can someone assist
02 Jun 2023, 00:22
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akshataxt
3. Which of the following, if true, would most clearly undermine the possible explanation for the whirling gas in M87 that is mentioned in the last sentence of the first paragraph?
(A) The stars in a star cluster at the center of M87 could exert a strong gravitational force without tearing the cluster apart.
(B) A cluster of stars at the center would preclude the existence of certain other astronomical phenomena that have been observed at the center of M87.
(C) The stars within many existing galaxies, such as NGC 4258, are more closely spaced than are the stars within the core of M87.
(D) Only one other galaxy has been observed to contain gas clouds whirling about its center as they do about the core of M87.
(E) The gravitational force of a cluster of a billion or so dim stars would be sufficient to cause a whirling ring of gas and dust to collect around the center of a galaxy.
What is the possible explanation for whirling gas?
"A few skeptics have argued that the concentration of mass necessary to explain the speed of the whirling gas is not necessarily a black hole: the concentration in M87 might be a cluster of a billion or so dim stars. "
That there could be cluster of a billion or so dim stars at the centre. Their force could explain the speed of the whirling gas.
We need to undermine this explanation i.e. weaken it. How do we do that? We say that it couldn't be a billion dim stars because ...
(B) A cluster of stars at the center would preclude the existence of certain other astronomical phenomena that have been observed at the center of M87.
It says that if there were a billion dim stars then certain other astronomical phenomena that have been observed at the center of M87 would not be there - they could not have taken place.
This weakens the explanation and hence is the answer.
(C) The stars within many existing galaxies, such as NGC 4258, are more closely spaced than are the stars within the core of M87.
This says that many other galaxies have stars which are even closer together (than the billion stars would have to be to be at the centre of M87).
To understand this, know that one issues why stars cannot be close together is that if they are too close to each other, they are likely to exert too much force on each other and merge or tear each other apart. So one issue with the explanation of the billion dim stars could be that the stars cannot be so close to each other to survive. But this option says that in other galaxies, they are even closer together and are still surviving. Hence, this supports the explanation, not weakens it.
Answer (B)
thelastskybender
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20 Jul 2023, 22:31
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AndrewN Can you please confirm whether my reasoning for choosing C in Q.4 was correct?
Most of the time the author of the passage was in reporting mode. The only time he showed some intention was when he mentioned that "Astronomers must infer the existence of black holes". Can we infer from this that the author is considering the possibility of some phenomenon? I mean, another potential option could be E, which says that the author was questioning a widely accepted explanation for an unusual phenomenon, but the author actually never questioned it. He just cited the opinions of a few sceptics and gave an example in which such a position was seriously undermined.
Most of the time the author of the passage was in reporting mode. The only time he showed some intention was when he mentioned that "Astronomers must infer the existence of black holes". Can we infer from this that the author is considering the possibility of some phenomenon? I mean, another potential option could be E, which says that the author was questioning a widely accepted explanation for an unusual phenomenon, but the author actually never questioned it. He just cited the opinions of a few sceptics and gave an example in which such a position was seriously undermined.
