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Astronomers theorize that a black hole forms when a massive object

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Astronomers theorize that a black hole forms when a massive object  [#permalink]

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Astronomers theorize that a black hole forms when a massive object shrinks catastrophically under its own gravity, leaving only a gravitational field so strong that nothing escapes it. Astronomers must infer the existence of black holes, which are invisible, from their gravitational influence on the visible bodies surrounding them. For example, observations indicate that gas clouds in galaxy M87 are whirling unusually fast about the galaxy’s center. Most astronomers believe that the large concentration of mass at the galaxy’s center is a black hole whose gravity is causing the gas to whirl. 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.

The same hypothesis might have been applied to the galaxy NGC 4258, but the notion of such a cluster’s existing in NGC 4258 was severely undermined when astronomers measured the speed of a ring of dust and gas rotating close to the galaxy’s center. From its speed, they calculated that the core’s density is more than 40 times the density estimated for any other galaxy. If the center of NGC 4258 were a star cluster, the stars would be so closely spaced that collisions between individual stars would have long ago torn the cluster apart.


1. The skeptics mentioned in the first paragraph would be most likely to agree with the astronomers mentioned in line 13 about which of the following statements concerning the galaxy M87?

(A) The speed of the gas whirling around the center of M87 is caused by a dense object that is not a black hole.

(B) The concentration of mass at the center of M87 is probably a large cluster of dim stars.

(C) The presence of a black hole at the center of M87 is the most likely explanation for the speed of the gas whirling about the galaxy’s core.

(D) The speed of the gas whirling around the center of M87 is caused by a large concentration of mass at the core of M87.

(E) The gravitational influence of a star cluster would not be strong enough to account for the speed of the gas whirling around the core of M87.



2. The passage asserts which of the following about the existence of black holes?

(A) Astronomers first speculated about the existence of black holes when they observed gas whirling around the center of a particular galaxy.

(B) Evidence used to argue for the existence of black holes is indirect, coming from their presumed effects on other astronomical bodies.

(C) Recent observations of certain astronomical bodies have offered proof.

(D) A considerable body of evidence suggests the existence of black holes, even though their behavior is not completely consistent with the laws of physics.

(E) Many astronomers are skeptical about certain recent evidence that has been used to argue for the existence of black holes.



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.



4. The passage is primarily concerned with

(A) explaining why a particular phenomenon is so rare

(B) criticizing a method used to gather data about a natural phenomenon

(C) considering possible instances of a particular phenomenon

(D) distinguishing among several different kinds of natural phenomena

(E) questioning a widely accepted explanation for an unusual phenomenon



FEATURE 24 June 1995
Obscure objects of Desire
By Marcus Chown

https://www.newscientist.com/article/mg14619834-200-obscure-objects-of-desire/

Originally posted by roopika2990 on 17 Feb 2013, 04:20.
Last edited by SajjadAhmad on 04 Aug 2019, 00:04, edited 6 times in total.
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New post 26 Feb 2013, 21:41
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Hello Aditya,

Q12:
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.

Notice the word "could". So there exist two possibilities.
1. They exert such a gravitational pull in which case, the cluster would be town apart. Since M87 has not been torn apart, this cluster does not exist.
2. They do not exert such a gravitational pull in which case M87 would not be torn apart and would exist. Since, it does exist, a star cluster could be located at its center.

In GMAT, you should pay special attention to words like could,might,may etc which give rise to a yes/no possibility. Often these statements have hidden information.

Hope this helps!

aditya111 wrote:
Kris01 wrote:

I am unable to understand the point where the first paragraph ends. I see two possible explanations for the whirling gas in M87, either the presence of a black hole at the center or the presence of a cluster of stars at the center. Could you please clarify where the first paragraph ends so that I could help you?

My guess would be that it ends at "the concentration in M87 might be a cluster of a billion or so dim stars." If this is so, the option that undermines this explanation would be b.
Reason: B states that if the center of the whirling gas consisted of a cluster of stars, then it would prevent certain other known astronomical phenomena from occuring at the center of the M87.

Could you please throw some more light on the question so that I could help you further?

swarman wrote:
Can u ( or ANYONE) pls answer the 12th question ?
need help :( :( :(


Why cant the 12th answer be A?
This statement clearly resolves the doubt which is cast in the passage right!
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Re: Astronomers theorize that a black hole forms when a massive object  [#permalink]

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New post 18 Feb 2013, 19:08
Hi Roopika2990,

A good way to approach such questions would be to read the questions first and then read the passage. It might save you time and also help you pinpoint the right answer during the first read itself.

10. We need to find out whether the skeptics would agree with the astronomers on something? If so, what would that be.
A. The speed of the gas whirling around the center of M87 is caused by a dense object that is not a black hole. // This is believed by the skeptics. However, the astronomers don't agree with this. They believe this is a black hole.
B. The concentration of mass at the center of M87 is probably a large cluster of dim stars. // This is again the belief held by skeptics and not by astronomers
C. The presence of a black hole at the center of M87 is the most likely explanation for the speed of the gas whirling about the galaxy’s core. // This is the belief of the astronomers and not skeptics.
D. The speed of the gas whirling around the center of M87 is caused by a large concentration of mass at the core of M87. // This is not directly mentioned as anyone's belief in particular. However this can be inferred from the passage. The passage suggests that the astronomers believe that this large concentration is due to a black hole while the skeptics believe that this large concentration is due to a cluster of stars located at the center. This is the right answer.
E. The gravitational influence of a star cluster would not be strong enough to account for the speed of the gas whirling around the core of M87. // This was proved by the astronomers with reference to NGC 4258

11. We need to find the fact that is asserted by the passage.
A. Astronomers first speculated about the existence of black holes when they observed gas whirling around the center of a particular galaxy. // The paragraph mentions that the astronomers believe that the gas whirling around the center of a particular galaxy is because of the presence of black holes at the center. However, this is not the first reason for speculation.
B. Evidence used to argue for the existence of black holes is indirect, coming from their presumed effects on other astronomical bodies. // This is the right answer. This is suggested in the lines 6-10.
C. Recent observations of certain astronomical bodies have offered proof. // The statement does not confirm what the proof is for. So we cannot be sure about this option or what the option mentions.
D. A considerable body of evidence suggests the existence of black holes, even though their behavior is not completely consistent with the laws of physics. // The movement of dust and gases suggest this. There is no considerable body of evidence. Hence, wrong
E. Many astronomers are skeptical about certain recent evidence that has been used to argue for the existence of black holes. //astronomers are skeptical about the existence of black holes.

Let me know if you have any more doubts.

roopika2990 wrote:
Astronomers theorize that a black
hole forms when a massive object
shrinks catastrophically under its own

Line

gravity, leaving only a gravitational

(5)

field so strong that nothing escapes it.
Astronomers must infer the existence
of black holes, which are invisible,
from their gravitational influence on
the visible bodies surrounding them.

(10)

For example, observations indicate
that gas clouds in galaxy M87 are
whirling unusually fast about the galaxy’s
center. Most astronomers
believe that the large concentration

(15)

of mass at the galaxy’s center is a
black hole whose gravity is causing
the gas to whirl. A few skeptics have
argued that the concentration of mass
necessary to explain the speed of the

(20)

whirling gas is not necessarily a black
hole: the concentration in M87 might
be a cluster of a billion or so dim stars.

The same hypothesis might have
been applied to the galaxy NGC 4258,

(25)

but the notion of such a cluster’s
existing in NGC 4258 was severely
undermined when astronomers measured
the speed of a ring of dust and
gas rotating close to the galaxy’s

(30)

center. From its speed, they calculated
that the core’s density is more
than 40 times the density estimated
for any other galaxy. If the center of
NGC 4258 were a star cluster, the

(35)

stars would be so closely spaced
that collisions between individual
stars would have long ago torn the
cluster apart.


Q10:
The skeptics mentioned in the first paragraph would be most likely to agree with the astronomers mentioned in line 13 about which of the following statements concerning the galaxy M87?
A. The speed of the gas whirling around the center of M87 is caused by a dense object that is not a black hole.
B. The concentration of mass at the center of M87 is probably a large cluster of dim stars.
C. The presence of a black hole at the center of M87 is the most likely explanation for the speed of the gas whirling about the galaxy’s core.
D. The speed of the gas whirling around the center of M87 is caused by a large concentration of mass at the core of M87.
E. The gravitational influence of a star cluster would not be strong enough to account for the speed of the gas whirling around the core of M87.

Q11:
The passage asserts which of the following about the existence of black holes?
A. Astronomers first speculated about the existence of black holes when they observed gas whirling around the center of a particular galaxy.
B. Evidence used to argue for the existence of black holes is indirect, coming from their presumed effects on other astronomical bodies.
C. Recent observations of certain astronomical bodies have offered proof.
D. A considerable body of evidence suggests the existence of black holes, even though their behavior is not completely consistent with the laws of physics.
E. Many astronomers are skeptical about certain recent evidence that has been used to argue for the existence of black holes.

Q12:
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.

DBB
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New post 25 Feb 2013, 11:46
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Hello,

I am unable to understand the point where the first paragraph ends. I see two possible explanations for the whirling gas in M87, either the presence of a black hole at the center or the presence of a cluster of stars at the center. Could you please clarify where the first paragraph ends so that I could help you?

My guess would be that it ends at "the concentration in M87 might be a cluster of a billion or so dim stars." If this is so, the option that undermines this explanation would be b.
Reason: B states that if the center of the whirling gas consisted of a cluster of stars, then it would prevent certain other known astronomical phenomena from occuring at the center of the M87.

Could you please throw some more light on the question so that I could help you further?

swarman wrote:
Can u ( or ANYONE) pls answer the 12th question ?
need help :( :( :(
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New post 26 Feb 2013, 20:06
Kris01 wrote:
Hello,

I am unable to understand the point where the first paragraph ends. I see two possible explanations for the whirling gas in M87, either the presence of a black hole at the center or the presence of a cluster of stars at the center. Could you please clarify where the first paragraph ends so that I could help you?

My guess would be that it ends at "the concentration in M87 might be a cluster of a billion or so dim stars." If this is so, the option that undermines this explanation would be b.
Reason: B states that if the center of the whirling gas consisted of a cluster of stars, then it would prevent certain other known astronomical phenomena from occuring at the center of the M87.

Could you please throw some more light on the question so that I could help you further?

swarman wrote:
Can u ( or ANYONE) pls answer the 12th question ?
need help :( :( :(


Why cant the 12th answer be A?
This statement clearly resolves the doubt which is cast in the passage right!
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Re: Astronomers theorize that a black hole forms when a massive object  [#permalink]

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New post 10 Aug 2016, 01:34
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3
Time taken 6 mins 30 seconds :? , including 2 mins to read

-The author talks about the black holes and how their existence is arrived at
-The author then discusses the objections of some skeptics to the existence of black holes
-The author eventually talks about how these skeptics could sometimes be wrong


1.
The skeptics and the astronomers only agree on a large concentration of mass existing at the core of M87. They disagree on what causes the large mass to exist at the core.
Answer D

2. “Astronomers must infer the existence of black holes, which are invisible, from their gravitational influence on the visible bodies surrounding them."
Answer B

3.
"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."

Option (B) clearly undermines the above explanation as it suggests the evidence of certain other astronomical phenomena.
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New post 24 Sep 2016, 15:05
1
Adding another question to it from the official GMAT Prep software

The passage is primarily concerned with
A explaining why a particular phenomenon is so rare
B criticizing a method used to gather data about a natural phenomenon
C considering possible instances of a particular phenomenon
D distinguishing among several different kinds of natural phenomena
E questioning a widely accepted explanation for an unusual phenomenon
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New post 22 Nov 2017, 01:57
keats wrote:
Adding another question to it from the official GMAT Prep software

The passage is primarily concerned with
A explaining why a particular phenomenon is so rare
B criticizing a method used to gather data about a natural phenomenon
C considering possible instances of a particular phenomenon
D distinguishing among several different kinds of natural phenomena
E questioning a widely accepted explanation for an unusual phenomenon


The OA for this one is indeed C. Just confirmed from the GMATPrep EP1.


It would be really great, if some moderator can add this question to the remaining sets of questions as well.

carcass, please can you add.

Thanks.
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New post 16 Jul 2018, 20:50
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Nived wrote:
Can someone explain Q10 (the first question). Multiple options seemed right to me here.


Nived, hope this helps:

1. The skeptics mentioned in the first paragraph would be most likely to agree with the astronomers mentioned in line 13 about which of the following statements concerning the galaxy M87?

"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."
before we go to the options, let's establish that skeptics have another theory to explain whirling gas clouds. The astronomers think the whirling is caused by a black hole.

(A) The speed of the gas whirling around the center of M87 is caused by a dense object that is not a black hole. <- nope. this is what the skeptics might believe. astronomers think it's caused by black hole. eliminate.

(B) The concentration of mass at the center of M87 is probably a large cluster of dim stars. <- this would go counter to what the astronomers believe; can't be a point of agreement. eliminate.

(C) The presence of a black hole at the center of M87 is the most likely explanation for the speed of the gas whirling about the galaxy’s core. <- this would go counter to what the skeptics believe (flip side of option B); can't be a point of agreement. eliminate.

(D) The speed of the gas whirling around the center of M87 is caused by a large concentration of mass at the core of M87. <- yes, both agree that there's something which is causing this swirling. keep.

(E) The gravitational influence of a star cluster would not be strong enough to account for the speed of the gas whirling around the core of M87. <- this would break skeptics claim; not mentioned in passage. eliminate.

Answer: D

Hope it helps.

Cheers!
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New post 29 Nov 2018, 01:33
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?


(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.

Dear All

Anyone , please can you advice reasons for C over B. I was confused between these two and chose C, reasons that in the passage " If the center of NGC 4258 were a star cluster, the stars would be so closely spaced that collisions between individual stars would have long ago torn the cluster apart. ". I inferred from this sentence that the finding was of not a star cluster but something else, if not black hole.

I thought this undermines the explanation.

Please can anyone advice, happy to be advised if you believe my understanding of the passage is not correct, I did find the last sentence confusing.
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New post 01 Dec 2018, 00:03
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proabhinav - hope this is helpful.

So this is a weakening question. 'if true' means we can use some imaginary situation, which may or may not true. before going for POE my pre-thoughts are --- I am looking for a choice, that weaken " the concentration in M87 might be a cluster of a billion or so dim stars.", In other words a choice that says that it is not true cause if this is true then some XYZ should also happen, but that is not. in general you want to look for existence of something you look for some evidence tto its presence. B is on these lines and I find it correct


(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. ---- Why this choice is not correct? Are you sure that if something is true on other galaxy then its true here. May be presence of a huge gravitational force is stabilizing that galaxy. All I am saying is this choice is not providing enough info to conclude.
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New post 22 Dec 2018, 03:51
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2. A. The paragraph mentions that the astronomers believe that the gas whirling around the center of a particular galaxy is because of the presence of black holes at the center. However, this is not the first reason for speculation.
B. This is the right answer. This is suggested in the lines 4-7. Hence, B is the answer.
C. The statement does not confirm what the proof is for. So we cannot be sure about this option or what the option mentions.
D. The movement of dust and gases suggest this. There is no considerable body of evidence suggesting the existence of black hole.
E. Astronomers are skeptical about the existence of black holes.
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New post 23 Dec 2018, 22:52
Skywalker18 wrote:

-The author talks about the black holes and how their existence is arrived at
-The author then discusses the objections of some skeptics to the existence of black holes
-The author eventually talks about how these skeptics could sometimes be wrong


Dear Experts workout Skywalker18 u1983
Could you please explain Question 4
4. The passage is primarily concerned with

(A) explaining why a particular phenomenon is so rare
(B)criticizing a method used to gather data about a natural phenomenon
(C)considering possible instances of a particular phenomeanon
(D)distinguishing among several different kinds of natural phenomena
(E)questioning a widely accepted explanation for an unusual phenomenon

I guess POE helps but I still can't 100% be sure how C is the primary purpose of the passage...
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New post 19 Jan 2019, 06:49
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There are some requests to post an answer how to arrive at C so I will try.
I choose E in the beginning to be honest but in review I got to C following this thinking:

My strategy in these general purpose questions of reading comprehension is to be very literal with the Verbs and Adjectives of each answer statement:

A. explaining why a particular phenomenon is so rare

"Explaining" seems odd to me here on first sight as they text is opposing two different theories, so this word does not seem to be optimal choise. In addition there is no explaination of the text why the Black holes are rare -> OUT

B. criticizing a method used to gather data about a natural phenomenon

"Criticizing" makes more sense, because the text is actually presenting two possible explanations for the Black Holes and then argues for one these explanations. However it has nothing to do with gathering data -> OUT

C. considering possible instances of a particular phenomeanon

"Considering" seems okay. It refers to the fact that the text is reflecting multiple theories for the creation of ONE particular phenomena, the Black Holes, so we are fine here. Besides the first Verb it is also important to be literal with adjective here.

D. distinguishing among several different kinds of natural phenomena

"Distinguishing" seems also okay, but we only have one phomena and not different kinds -> OUT

E. questioning a widely accepted explanation for an unusual phenomenon

"Questioning" seems fine here. The next adjective is the "widely accepeted". Seems also okay as "most astronomers" believe that the large concentration of mass at the galaxy's center is a black hole whose gravity is causing the gas to whirl.
However the text never mentions that this phenomenon is unusual. We are assuming that because we migh have heard that black holes are not so common, but the text never explictly states that so -> OUT

Would be happy to get your opinion on this!
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New post 08 Mar 2019, 02:47
ssmissiongmat wrote:
Hi, can anyone help analyse why in Q4 'C' is right and also, why 'E' is incorrect?


There is no questionable intent through the whole passage. It just give 2 possible observations about black holes. So C is the correct choice.
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