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 D 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 B 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 B 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 C 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/

Last visit was: 19 Nov 2025, 14:41

It is currently 19 Nov 2025, 14:41

Toolkit

Reading Comprehension (RC)

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Go to My Error Log Learn more

Request Expert Reply

Confirm Cancel

Nov 20
UCR MBA Impact - Live Q&A with UCR AdCom & Student
07:30 AM PST
-
08:30 AM PST
Learn what truly sets the UC Riverside MBA apart and how it helps in your professional growth
Nov 22
GMAT RC Masterclass
11:00 AM IST
-
01:00 PM IST
Do RC/MSR passages scare you? e-GMAT is conducting a masterclass to help you learn – Learn effective reading strategies Tackle difficult RC & MSR with confidence Excel in timed test environment
Nov 23
Conquer Algebra on the GMAT Focus Edition
11:00 AM IST
-
01:00 PM IST
Attend this free GMAT Algebra Webinar and learn how to master the most challenging Inequalities and Absolute Value problems with ease.
Nov 25
Try OnDemand GMAT Masterclass
10:00 AM EST
-
11:00 AM EST
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors.

Back to Forum

Create Topic

Astronomers theorize that a black hole forms when a massive object

1 2 3 4

datemike

Current Student

Joined: 03 May 2020

Last visit: 19 Nov 2021

Posts: 29

Own Kudos:

[1]

Given Kudos: 47

Location: India

Schools: ISB '23 (A)

GMAT 1: 700 Q49 V36 Verified score

GPA: 3.63

Schools: ISB '23 (A)

GMAT 1: 700 Q49 V36 Verified score

Posts: 29

Kudos: 11

[1]

09 Jul 2021, 22:41

Kudos

Bookmarks

omersoylu

Hello,
About question 4:
I was able to eliminate A,D, and E. But between B and C I think the answer should be B.
If we look the meaning of each word in the options in option B : the verb CRITICIZE is OK. Because the passage has an opinion and implies that sceptics are wrong. METHOD is not OK but also NOT SO BAD. Because spectics are using another method to explain the phenomenon. ( that method is wrong).
Option C : The verb CONSIDER is NEUTRAL. It implies that passage is just trying to explain or evaluate something. That is not the purpose of the passage. POSSIBLE INSTANCES is WRONG. Because assuming that concentration of gases are not black holes but clusters is an EXPLANATION.
To sum up, I think if we compare B and C in detail, B makes more sense.
Can you please explain what is wrong with my method?

Thank you

Hello.
"criticize" is too strong a tone for primary purpose here in my opinion. If you look closely, the 1st para ends with the claim that few skeptics have argued... this is not the author's opinion but a statement he simply makes. Hence the first para doesn't imply the tone of criticism. The second para on the other hand may, because it says that considering this method in a different example severely undermined the hypotheses. However for primary concern questions, the best answer choice is one which covers tone/scope of all paragraphs.
Secondly, a major error here is that this is NOT a method used to gather data as option B suggests. There is no gathering of data happening.

Possible instances is correct. Instances implies different cases/examples. Here the author is considering 2 of these- one for M87 and the other for NGC4258. Hence this answer choice covers the scope and tone of both paras.

zoezhuyan

Joined: 17 Sep 2016

Last visit: 11 Nov 2024

Posts: 418

Own Kudos:

Given Kudos: 147

Posts: 418

Kudos: 94

09 Nov 2021, 00:45

Kudos

Bookmarks

AndrewN

mSKR

Quote:

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?

Quote:

(A) The stars in a star cluster at the center of M87 could exert a strong gravitational force without tearing the cluster apart.

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.

Basically we need to weaken the hypothesis that the concentration in M87 might be a cluster of a billion or so dim stars (Let’s say it cluster theory). In other words, if we can infer that it is black hole then also it undermines the cluster theory.

The last lines of passage says:
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.

It means that starts can be closely spaced due to black hole. If no black hole then cluster would be torn apart

With this understanding when we read A, it says stars could exert a strong gravitational force without tearing cluster apart. So it means it is not due to concentration of billion or so dim stars but because of black hole or other phenomenon; but definitely not due to cluster theory.

With this understanding, why should I not choose A?

Please suggest .

Quote:

(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.

Can I say E supports the conclusion drawn in the last lines of 1st passage instead of weakening? It is actually supporting the cluster theory , is not it? Kindly give your comments.

CrackVerbalGMAT GMATNinja @AndrewN : please give your opinion.
( sorry AndrewN for tagging you again for another passage in a day)

Hello again, mSKR. Both (A) and (E) would strengthen the notion that the whirling gas in M87 could be the result of a cluster of a billion or so dim stars, because each answer choice names a star cluster as the agent that corroborates the astronomical observations. You are correct in saying that you want to weaken the star cluster hypothesis, but you are looking in the wrong place.

Quote:

(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.

If a star cluster would preclude or rule out the possibility of other established astronomical observations, then we can deduce that a star cluster must not exist at the center of the galaxy, as speculated by a few skeptics. If you did not understand the word preclude, I can see how you would overlook this one, but this answer choice is a clear weakener to what we are being asked about, the star cluster hypothesis.

- Andrew

dear AndrewN, and other GMATNinja, GMATNinjaTwo, VeritasKarishma,

Quote:

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

.
if there is only one other galaxy that has been observed to containers clouds whirling about its center as they do about the core of M87, then will D implies this phenomenon is unrepresentative ? then D weakens the possible explanation ?

AndrewN

Volunteer Expert

Joined: 16 May 2019

Last visit: 29 Mar 2025

Posts: 3,502

Own Kudos:

7,511

[2]

Given Kudos: 500

Expert

Expert reply

Posts: 3,502

Kudos: 7,511

[2]

09 Nov 2021, 14:26

Kudos

Bookmarks

zoezhuyan

dear AndrewN, and other GMATNinja, GMATNinjaTwo, VeritasKarishma,

Quote:

Hello, zoezhuyan. The problem I see with answer choice (D) above is that it does not address the possible explanation in question. Look at the last line of the first paragraph again:

Quote:

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 explanation given is that the concentration [of mass] in M87 might be a cluster of a billion or so dim stars rather than a black hole. You should know from CR that to undermine or weaken an argument or explanation, you need to stick to that exact argument or explanation. Thus, we should be looking for an answer choice that touches on this star cluster hypothesis and diminishes its plausibility. Choice (D) attacks the observation itself—that gas is whirling about the center of the galaxy—and that observation merely serves as a premise for the explanation. In short, choice (D) attacks the wrong target. I have discussed choice (B) more in my earlier post, which you quoted above. I hope that you can appreciate why (D) is NOT the answer, though.

Thank you for thinking to ask.

- Andrew

Roonsta

Joined: 11 Mar 2017

Last visit: 07 Jan 2022

Posts: 25

Own Kudos:

Given Kudos: 53

Location: United States

GMAT 1: 710 Q47 V40 Verified score

GMAT 2: 670 Q49 V33 (Online) Verified score

GMAT 3: 710 Q47 V41 Verified score

GPA: 3.5

WE:Investment Banking (Healthcare/Pharmaceuticals)

GMAT 3: 710 Q47 V41 Verified score

Posts: 25

Kudos: 33

26 Dec 2021, 16:46

Kudos

Bookmarks

Hi - so why is it B over E for Q3 (i.e., the one with PRECLUDE in the answer choices)? Where the heck is there evidence in the passage suggesting that precluding other astronomical phenomena in the center would weaken the hypothesis of the end of the first paragraph (b/c I didn't find it)? Don't believe we've gotten a great answer here.

HWPO

Joined: 11 May 2020

Last visit: 02 Jul 2025

Posts: 121

Own Kudos:

Given Kudos: 146

Posts: 121

Kudos: 18

27 Feb 2022, 15:17

Kudos

Bookmarks

How would you guys go about reading a passage like this? On one hand there are too many details and it's supposedly preferable to stick to the MAIN IDEA and STRUCTURE. On the other hand, details are a significant, major part of the passage and it seems almost impossible to read the passage without pausing to think about the details and jot them down.

GMATNinja KarishmaB

KarishmaB

Tutor

Joined: 16 Oct 2010

Last visit: 19 Nov 2025

Posts: 16,267

Own Kudos:

77,000

[2]

Given Kudos: 482

Location: Pune, India

Expert

Expert reply

Posts: 16,267

Kudos: 77,000

[2]

27 Feb 2022, 22:08

Kudos

Bookmarks

HWPO

HWPO - No need to jot anything down. The passage is a short but dense science passage. Usually, for such short dense passages, a good approach is to read them twice. A second reading helps one understand a lot that one misses in the first read because the topic and logic are unfamiliar. Since the passage is short, it doesn't take a lot of time.
Also, it will be very helpful to familiarise yourself with different topics in science, business, history, economics etc. Put extra efforts in the subjects that are beyond your field of work/interest etc

HWPO

Joined: 11 May 2020

Last visit: 02 Jul 2025

Posts: 121

Own Kudos:

Given Kudos: 146

Posts: 121

Kudos: 18

28 Feb 2022, 20:19

Kudos

Bookmarks

KarishmaB

HWPO

That's new - reading a passage twice. I will start doing that in short passages like this.

Thank you so much I really appreciate this!

rsrighosh

Joined: 13 Jun 2019

Last visit: 11 Dec 2022

Posts: 188

Own Kudos:

132

[1]

Given Kudos: 645

GMAT 1: 490 Q42 V17 Verified score

GMAT 2: 550 Q39 V27 Verified score

GMAT 3: 630 Q49 V27 Verified score

Posts: 188

Kudos: 132

[1]

25 Apr 2022, 03:52

Kudos

Bookmarks

GMATNinja KarishmaB

Could you please help with the Generic question I have:-

Considering 4th question as the example:-

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

How will I find the right tone of a passage.
How will I know that the author is criticising(B) or considering(C) or explaining(A)
Is there any key word that can help us understand the tone of passage.

KarishmaB

Tutor

Joined: 16 Oct 2010

Last visit: 19 Nov 2025

Posts: 16,267

Own Kudos:

77,000

[4]

Given Kudos: 482

Location: Pune, India

Expert

Expert reply

Posts: 16,267

Kudos: 77,000

[4]

25 Apr 2022, 04:20

Kudos

Bookmarks

rsrighosh

We cannot rely on keywords to tell us the tone. An explanation passage could use a word of criticism. A consideration passage could explain a particular method etc.
The words after 'criticising' or 'considering' or 'explaining' are important to get the primary purpose.

To get the tone, explanation passage will give you the details of the workings of something (this is how A happens, this is why B happens, and then this happens etc). A criticism will point out the flaws. A cautious optimism will reflect a hopeful attitude toward the future etc.
Note that tone is not reflected in one or two words; it is the way the author handles the subject matter. It is what the author says, not really how he says it since GMAT passages will rarely use intense (positive or negative) words. The words used will be well measured, objective and/or evaluative.

Tanchat

Joined: 31 Jan 2020

Last visit: 20 Jun 2023

Posts: 222

Own Kudos:

Given Kudos: 139

Posts: 222

Kudos: 20

03 Jul 2022, 01:59

Kudos

Bookmarks

CrackverbalGMAT

shanks2020

Sorry, but i did not get the logic behind it. Let me explain.
The passage hypothesize that the center mass might be cluster of stars.
Now this option B mentions that THIS star cluster rules out CERTAIN other phenomenon observed at the center of M87.
If i look closely, it does not mention any other phenomenon or all phenomenon. That means that "Certain" could be anything.
Moreover, it does not rule out that that cluster of stars are not those which are causing the whirling of gas. In fact, it strenghtens it by stating something else is not there/so it is like ruling out alternate causes.
AndrewN may be you can provide your thoughts too!!!
But the question asks to undermine the statement.

Hi

You are absolutely right that that "Certain" could be anything. However, we do know something for sure about it - that it has been "observed", and therefore must exist for sure. Now, let's call these "certain phenomena" X.

We know that X exists for sure. But, as per option (B), if there were a "cluster of stars at the center of M87" (which, let's note, is only a hypothetical scenario), then X should not exist ("...would preclude the existence of certain other astronomical phenomena..."). Therefore, this undermines the theory that there is a cluster of stars at the center of M87. It takes this simple structure:

If A --> B then (not B) --> (not A)

As per option (B), if A (ie; cluster of stars), then (not X) (ie; no "certain phenomena")
We know X exists [ie; not (not X) is true], therefore (not A) (no cluster of stars) must be true

Also, no alternative explanation is being ruled out. The "cluster of stars" hypothesis is presented to explain the swirling gas. What is being ruled out in option (B) is X - which are not related to the swirling gas in any way.

Hope this clarifies.

CrackverbalGMAT

Could you pls help why C is incorrect?

In choice (C), The stars within many existing galaxies, such as NGC 4258, are more closely spaced than are the stars within the core of M87
And the passage said : 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.
Even, the NGC 4258 has more closely spaced than are the starts within the core of M87. Then, it would be impossible that M87 contains a cluster of a billion or so dim stars.
Then, it literally undermines.

Tanchat

Joined: 31 Jan 2020

Last visit: 20 Jun 2023

Posts: 222

Own Kudos:

[1]

Given Kudos: 139

Posts: 222

Kudos: 20

[1]

03 Jul 2022, 02:00

Kudos

Bookmarks

Dear Experts, @AndewN GMATNinja GMATNinjatwo CrackverbalGMAT

Question no. 3

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.

Could you pls help why C is incorrect?

In choice (C), The stars within many existing galaxies, such as NGC 4258, are more closely spaced than are the stars within the core of M87
And the passage said : 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.
Even, the NGC 4258 has more closely spaced than are the starts within the core of M87. Then, it would be impossible that M87 contains a cluster of a billion or so dim stars.
Then, it literally undermines.

AndrewN

Volunteer Expert

Joined: 16 May 2019

Last visit: 29 Mar 2025

Posts: 3,502

Own Kudos:

7,511

[3]

Given Kudos: 500

Expert

Expert reply

Posts: 3,502

Kudos: 7,511

[3]

03 Jul 2022, 04:05

Kudos

Bookmarks

Tanchat

Hello, Tanchat. I seem to have touched on just about every other answer choice in question 3 in earlier posts, but not (C). I am not following the logic at the end of your post. I took the same line of the passage as potential support for the alternative (star cluster) hypothesis. Why? Because if the stars in NGC 4258 are more closely spaced than are the stars within the core of M87, and if the stars within NGC 4258 would be so closely spaced that collisions between individual stars would have long ago torn the cluster apart, then we can infer that a galaxy such as M87—one that contains stars that are spaced farther apart—might not be torn apart by collisions between individual stars. There would be no evidence to challenge the star cluster hypothesis.

Does that make sense?

- Andrew

Tanchat

Joined: 31 Jan 2020

Last visit: 20 Jun 2023

Posts: 222

Own Kudos:

Given Kudos: 139

Posts: 222

Kudos: 20

03 Jul 2022, 10:30

Kudos

Bookmarks

AndrewN

Tanchat

AndrewN
Thank you so much. I wrongly understood that "more closely spaced" = farther the distance among stars.
Then, The stars in NGC 4258 are more closely spaced than are the stars within the core of M87 doesn't help to undermine.
But if, we changed "more closely spaced than" -> "less closely space than", it would help, right?

AndrewN

Volunteer Expert

Joined: 16 May 2019

Last visit: 29 Mar 2025

Posts: 3,502

Own Kudos:

7,511

[1]

Given Kudos: 500

Expert

Expert reply

Posts: 3,502

Kudos: 7,511

[1]

03 Jul 2022, 11:13

Kudos

Bookmarks

Tanchat

Hello again, Tanchat. Yes, if we knew from the answer choice that the stars within M87 were more densely packed (i.e. had less space between each other) than those in NGC 4258, then given the same line from the passage that we both quoted earlier, we could reason that the star cluster hypothesis was less likely. (Note that undermine does not demand irrefutable proof against something.)

Thank you for following up.

- Andrew

Tanchat

Joined: 31 Jan 2020

Last visit: 20 Jun 2023

Posts: 222

Own Kudos:

Given Kudos: 139

Posts: 222

Kudos: 20

03 Jul 2022, 11:20

Kudos

Bookmarks

AndrewN

Tanchat

AndrewN
Thank you so much. I can eliminate all wrong options A,C,D,E

Can I ask one last question?

In (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.

Does the existence of certain other astronomical phenomena include “BLACK HOLE”?

From the phrase : the existence of certain other astronomical phenomena that have been observed at the center of M87. I’m not sure whether “SO DIM STARS” can be observed or not.

Posted from my mobile device

AndrewN

Volunteer Expert

Joined: 16 May 2019

Last visit: 29 Mar 2025

Posts: 3,502

Own Kudos:

7,511

[1]

Given Kudos: 500

Expert

Expert reply

Posts: 3,502

Kudos: 7,511

[1]

03 Jul 2022, 12:09

Kudos

Bookmarks

Tanchat

All right, last one. In the context of the sentence, certain other astronomical phenomena that have been observed refers to known or established phenomena. We cannot pick and choose which phenomena we want that description to apply to. If there is even a debate about what constitutes the large concentration of mass at the galaxy’s center—a black hole, a star cluster, or some other, unnamed body about which we can only speculate—then we cannot say exactly which phenomena are covered (most likely the whirling gas, since there is no apparent disagreement on this observation), only which ones are not.

- Andrew

kittle

Joined: 11 May 2021

Last visit: 19 Nov 2025

Posts: 318

Own Kudos:

161

Given Kudos: 618

Products:

Posts: 318

Kudos: 161

23 Nov 2022, 13:32

Kudos

Bookmarks

@GMATNinja- can you explain the below question? Really need help.

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

tanishkamishra

Joined: 11 Dec 2022

Last visit: 16 Mar 2023

Posts: 6

Given Kudos: 38

Posts: 6

Kudos: 0

19 Jan 2023, 06:12

Kudos

Bookmarks

Dear Experts

I couldn't get question 1, 2 and 3 right. I also found it very difficult to understand the answer choices, and the major reason why I found it difficult was because it seemed very technical to me and it puzzled me. Request you to explain the above questions and the right approach for attempting RC questions when the questions seem very technical.

Thankyou

KarishmaB

Tutor

Joined: 16 Oct 2010

Last visit: 19 Nov 2025

Posts: 16,267

Own Kudos:

77,000

Given Kudos: 482

Location: Pune, India

Expert

Expert reply

Posts: 16,267

Kudos: 77,000

19 Jan 2023, 22:16

Kudos

Bookmarks

tanishkamishra

A fairly technical passage is usually short, so that's the silver lining.
It's a good idea to be well read and it's never too late to start. If you know a bit about the topic at hand, it becomes far easier to understand.

Question 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?

This is what we are given about the skeptics:
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.

Many astronomers believe that it is a black hole at the centre of M87 that is causing the gas to swirl around but the skeptics say that it is not necessary. It could be a cluster of stars (not that it is but it could be).
Basically, astronomers say that this is A. But skeptics say that it is not necessary. It could be B too. So the skeptics are not saying that it is not A. They are not saying that it is B. They are just saying that either is possible.

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

They don't say that it is not a black hole. They say that it is not necessarily a black hole. It could be a black hole or it could be something else too.

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

They don't say that it is a large cluster of dim stars. They say that it could be. It is one of the possible explanations for the gas swirling as is a black hole. Basically there is something with heavy mass concentration.

(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.

They say that a black hole is not the only explanation, not that it is the most likely explanation.

(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.

Correct. They do agree that there is large concentration of mass at the core of M87. They just believe that it may not necessarily be because of a black hole. The large concentration of mass could be a cluster of stars too (which is also a large concentration of mass).

(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.

The skeptics believe that it could be a cluster of stars so they believe that the gravitational influence of a star cluster WOULD BE strong enough to account for the speed of the gas whirling.

Answer (D)

KarishmaB

Tutor

Joined: 16 Oct 2010

Last visit: 19 Nov 2025

Posts: 16,267

Own Kudos:

77,000

Given Kudos: 482

Location: Pune, India

Expert

Expert reply

Posts: 16,267

Kudos: 77,000

Updated on: 19 Jan 2023, 22:27

Originally posted by KarishmaB on 19 Jan 2023, 22:21.
Last edited by KarishmaB on 19 Jan 2023, 22:27, edited 1 time in total.

Kudos

Bookmarks

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.

No information is given on when they FIRST speculated about the existence of black holes.

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

Correct.

Second line of the passage:
Astronomers must infer the existence of black holes, which are invisible, from their gravitational influence on the visible bodies surrounding them.

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

It is still speculation as per the passage.

(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.

We are not given that there is a 'considerable body of evidence' and nothing about 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.

The passage says that a few astronomer are skeptical. Also, is this recent evidence, we don't know.

Answer (B)