New observations about the age of some globular clusters in our Milky

Question

New observations about the age of some globular clusters in our Milky Way galaxy have cast doubt on a long-held theory about how the galaxy was formed. The Milky Way contains about 125 globular clusters (compact groups of anywhere from several tens of thousands to perhaps a million stars) distributed in a roughly spherical halo around the galactic nucleus. The stars in these clusters are believed to have been born during the formation of the galaxy, and so may be considered relics of the original galactic nebula, holding vital clues to the way the formation took place.

The conventional theory of the formation of the galaxy contends that roughly 12 to 13 billion years ago the Milky Way formed over a relatively short time (about 200 million years) when a spherical cloud of gas collapsed under the pressure of its own gravity into a disc surrounded by a halo. Such a rapid formation of the galaxy would mean that all stars in the halo should be very nearly the same age.

However, the astronomer Michael Bolte has found considerable variation in the ages of globular clusters. One of the clusters studied by Bolte is 2 billions years older than most other clusters in the galaxy, while another is 2 billion years younger. A colleague of Bolte contends that the cluster called Palomar 12 is 5 billion years younger than most other globular clusters.

To explain the age differences among the globular clusters, astronomers are taking a second look at “renegade” theories. One such newly fashionable theory, first put forward by Richard Larson in the early 1970’s, argues that the halo of the Milky Way formed over a period of a billion or more years as hundreds of small gas clouds drifted about, collided, lost orbital energy, and finally collapsed into a centrally condensed elliptical system. Larson’s conception of a “lumpy and turbulent” protogalaxy is complemented by computer modeling done in the 1970’s by mathematician Alan Toomre, which suggests that closely interacting spiral galaxies could lose enough orbital energy to merge into a single galaxy.   1 
 1. The passage is primarily concerned with discussing

(A) the importance of determining the age of globular clusters in assessing when the Milky Way galaxy was formed 
(B) recent changes in the procedures used by astronomers to study the formation of the Milky Way galaxy 
(C) current disputes among astronomers regarding the size and form of the Milky Way galaxy 
(D) the effect of new discoveries regarding globular clusters on theories about the formation of the Milky Way galaxy 
(E) the origin, nature, and significance of groups of stars known as globular clusters

2 
 2. According to the passage, one way in which Larson's theory and the conventional theory of the formation of the Milky Way galaxy differ is in their assessment of the

(A) amount of time it took to form the galaxy 
(B) size of the galaxy immediately after its formation 
(C) the particular gases involved in the formation the galaxy 
(D) importance of the age of globular clusters in determining how the galaxy was formed 
(E) shape of the halo that formed around the galaxy

3 
 3. Which of the following, if true, would be most useful in supporting the conclusions drawn from recent observations about globular clusters?

(A) There is firm evidence that the absolute age of the Milky Way galaxy is between 10 and 17 billion years. 
(B) A survey reveals that a galaxy close to the Milky Way galaxy contains globular clusters of ages close to the age of Palomar 12. 
(C) A mathematical model proves that small gas clouds move in regular patterns. 
(D) Space probes indicate that the stars in the Milky Way galaxy are composed of several different types of gas. 
(E) A study of over 1,500 individual stars in the halo of the Milky Way galaxy indicates wide discrepancies in their ages.

4 
 4. If Bolte and his colleague are both correct, it can be inferred that the globular cluster Palomar 12 is approximately

(A) 5 billion years younger than any other cluster in the galaxy 
(B) the same age as most other clusters in the galaxy 
(C) 7 billion years younger than another cluster in the galaxy 
(D) 12 billion years younger than most other clusters in the galaxy 
(E) 2 billion years younger than most other clusters in the galaxy

5 
 5. The passage suggests that Toomre's work complements Larson's theory because it

(A) specifies more precisely the time frame proposed by Larson 
(B) subtly alters Larson's theory to make it more plausible 
(C) supplements Larson's hypothesis with direct astronomical observations 
(D) provides theoretical support for the ideas suggested by Larson 
(E) expands Larson's theory to make it more widely applicable

6 
 6. Which of the following most accurately states a finding of Bolte's research, as described in the passage?

(A) The globular clusters in the Milky Way galaxy are 2 billion years older than predicted by the conventional theory. 
(B) The ages of at least some globular clusters in the Milky Way galaxy differ by at least 4 billion years. 
(C) One of the globular clusters in the Milky Way galaxy is 5 billion years younger than most others. 
(D) The globular clusters in the Milky Way galaxy are significantly older than the individual stars in the halo. 
(E) Most globular clusters in the Milky Way galaxy are between 11 and 15 billion years old.

7 
 7. The author of the passage puts the word "renegade" (line 29) in quotation marks most probably in order to

(A) emphasize the lack of support for the theories in question 
(B) contrast the controversial quality of the theories in question with the respectable character of their formulators 
(C) generate skepticism about the theories in question 
(D) ridicule the scientists who once doubted the theories in question 
(E) indicate that the theories in question are no longer as unconventional as they once seemed

GMATNinja · Accepted Answer

The word "renegade" implies that those theories were not conventional or commonly accepted. This does not necessarily imply that those theories lacked support.

For example, there might be strong support for a theory claiming that eating hot dogs every day is good for your health. But if most people reject that theory, it would still be considered "renegade".

The author puts the word "renegade" in quotes to emphasize that those theories are gaining acceptance. For example, imagine that new evidence suggested that eating broccoli and carrots, foods commonly viewed as healthy, was in fact bad for your health. You might then say:

I no longer want to eat "healthy" foods like broccoli and carrots.

The use of the quotation marks emphasizes that those foods were once accepted as healthy but that this view is changing. The same thing applies in this passage. The theories were once considered "renegade", but now they are becoming less and less "renegade".

I hope that helps!

GMATNinja · Answer

Choice (C) states a finding of Bolte's colleague, not of Bolt himself:

I hope this helps!

PrashantPonde · Answer

3. Which of the following, if true, would be most useful in supporting the conclusions drawn from recent observations about globular clusters?

(A) There is firm evidence that the absolute age of the Milky Way galaxy is between 10 and 17 billion years. 
(B) A survey reveals that a galaxy close to the Milky Way galaxy contains globular clusters of ages close to the age of Palomar 12. 
(C) A mathematical model proves that small gas clouds move in regular patterns. 
(D) Space probes indicate that the stars in the Milky Way galaxy are composed of several different types of gas. 
(E) A study of over 1,500 individual stars in the halo of the Milky Way galaxy indicates wide discrepancies in their ages.

To address this question, our primary objective is to analyze what findings can help strengthen the conclusion the most.

The conclusion (revealed from the recent observations about globular clusters):-
Inside the same galaxy, there can be considerable variation in the ages of globular clusters. The conventional theory, which states that the "rapid" formation of the galaxy would mean stars in the halo should be nearly the same age, is  NOT  true.

Choice (B) A survey reveals that a galaxy close to the Milky Way galaxy contains globular clusters of ages close to the age of Palomar 12. 
-- This survey can only reveal the age statistics of one edge of the age spectrum. i.e. as Palomar 12 is 5 billion years younger than most of the stars then,  these stars are likely to be around the same age , hence will not help to the conclusion by studying the stars having wide spectrum of ages.

Choice (E) A study of over 1,500 individual stars in the halo of the Milky Way galaxy indicates wide discrepancies in their ages.
This study can provide statistics of the  stars which have "wide" discrepancies in their ages , hence can help solidify the new observations that these  stars can have considerable variation in ages . (phrase "wide" discrepancy in this context means "wide" variations).

HTH

mbaiseasy · Answer

4. If Bolte and his colleague are both correct, it can be inferred that the globular cluster Palomar 12 is approximately

(A) it is clear. The passage says 5 billion years younger than most and not all. False.
(B) false also. It is 5 billion yrs younger than most.
(C) correct. If the Palomar 12 is 5 billion years younger than most. Then there is one cluster 2 billion years older and another 2 billion yrs younger than most. Thenit follows that Palomar is 7 billion yrs older than another cluster.
(D) 12 billion years younger... Heck no!
(E) 5 billion younger than most and not 2 billion years. False again.

5. The passage suggests that Toomre's work complements Larson's theory because it 
(A) no precise time frame discussed in the passage
(B) no subtle alteration by Toomre's work...
(C) the support given was through a computer model not astronomical ...
(D) provides theoretical support for the ideas suggested by Larson ... correct.
(E) no applicability discussed

6. Which of the following most accurately states a finding of Bolte's research, as described in the passage?

(B) The ages of at least some globular clusters in the Milky Way galaxy differ by at least 4 billion years.

I did not go through all the answers but B is obviously correct. There are some 2 billion years older than most or 2 billion yrs younger than most. Thus, gap is 4 billion years. At least some is safe wording.

7. The author of the passage puts the word "renegade" (line 29) in quotation marks most probably in order to

Renegade to me I thought since they find some findings against conventional theory. They look to renegade theory. Perhaps, what once thought wrong old be actually right.

(E) indicate that the theories in question are no longer as unconventional as they once seemed

srikanth9502 · Answer

In Question 7, I am confused between option A and E. Could you please explain why A is wrong and E is correct?

ingeniouseerat · Answer

why the answer is not C for Question no 6?

ShashankDave · Answer

I got Q5 wrong. I chose E as my answer. Somebody please help. The computer models suggest that the ideas of the scientist also apply to spiral galaxies not just within a galaxy. This clearly means that there is a wider applicability. I don't disagree with the OA but I was confused between the two and got this wrong. Is my approach wrong here? Does "wide applicability" need to be explicitly stated in the passage for E to be correct? what did I do wrong?

gmatexam439 · Answer

1. The passage is primarily concerned with discussing

(A) the importance of determining the age of globular clusters in assessing when the Milky Way galaxy was formed - Incorrect. The passage is discussing various theories 
(B) recent changes in the procedures used by astronomers to study the formation of the Milky Way galaxy - Incorrect 
(C) current disputes among astronomers regarding the size and form of the Milky Way galaxy - No disputes have been discussed 
(D) the effect of new discoveries regarding globular clusters on theories about the formation of the Milky Way galaxy - Correct. Various theories have been discussed and their effects on others have been pointed out. 
(E) the origin, nature, and significance of groups of stars known as globular clusters - Incorrect

2. According to the passage, one way in which Larson's theory and the conventional theory of the formation of the Milky Way galaxy differ is in their assessment of the

(A) amount of time it took to form the galaxy - Correct. Conventional theory states that the galaxy was formed in short time while the other one states that the galaxy was formed in billions of years 
(B) size of the galaxy immediately after its formation - irrelevent 
(C) the particular gases involved in the formation the galaxy - irrelevant 
(D) importance of the age of globular clusters in determining how the galaxy was formed - Out of scope 
(E) shape of the halo that formed around the galaxy - Irrelevant

3. Which of the following, if true, would be most useful in supporting the conclusions drawn from recent observations about globular clusters?

(A) There is firm evidence that the absolute age of the Milky Way galaxy is between 10 and 17 billion years. - This is an exaggerated choice 
(B) A survey reveals that a galaxy close to the Milky Way galaxy contains globular clusters of ages close to the age of Palomar 12. - Other galaxy? Incorrect 
(C) A mathematical model proves that small gas clouds move in regular patterns. - Model doesn't talk about regular patterns 
(D) Space probes indicate that the stars in the Milky Way galaxy are composed of several different types of gas. - types of gases? incorrect 
(E) A study of over 1,500 individual stars in the halo of the Milky Way galaxy indicates wide discrepancies in their ages. - Correct.

4. If Bolte and his colleague are both correct, it can be inferred that the globular cluster Palomar 12 is approximately

(A) 5 billion years younger than any other cluster in the galaxy - any? exaggerated 
(B) the same age as most other clusters in the galaxy - same age? out of scope 
(C) 7 billion years younger than another cluster in the galaxy - Correct. (5+2) 
(D) 12 billion years younger than most other clusters in the galaxy - 12? Incorrect 
(E) 2 billion years younger than most other clusters in the galaxy - Not 2 but 5

5. The passage suggests that Toomre's work complements Larson's theory because it

(A) specifies more precisely the time frame proposed by Larson - time?  
(B) subtly alters Larson's theory to make it more plausible - alters? 
(C) supplements Larson's hypothesis with direct astronomical observations - astronomical observations? 
(D) provides theoretical support for the ideas suggested by Larson - Correct. 
(E) expands Larson's theory to make it more widely applicable - expand?

6. Which of the following most accurately states a finding of Bolte's research, as described in the passage?

(A) The globular clusters in the Milky Way galaxy are 2 billion years older than predicted by the conventional theory. - incorrect 
(B) The ages of at least some globular clusters in the Milky Way galaxy differ by at least 4 billion years. - correct. (2+2) 
(C) One of the globular clusters in the Milky Way galaxy is 5 billion years younger than most others. - Incorrect. This was Bolte's college's observation 
(D) The globular clusters in the Milky Way galaxy are significantly older than the individual stars in the halo. - out of scope 
(E) Most globular clusters in the Milky Way galaxy are between 11 and 15 billion years old. - exaggerated

7. The author of the passage puts the word "renegade" (line 29) in quotation marks most probably in order to
  --I didn't know the meaning of "renegade" but solved it using the context of the passage.  
(A) emphasize the lack of support for the theories in question - A mathematical model supports a theory. Incorrect 
(B) contrast the controversial quality of the theories in question with the respectable character of their formulators - Character of the inventors is not discussed. Incorrect 
(C) generate skepticism about the theories in question - The passage is not generating any skepticism regarding the theories. 
(D) ridicule the scientists who once doubted the theories in question - The last para is definitely not ridiculing anyone 
(E) indicate that the theories in question are no longer as unconventional as they once seemed - Correct. Only remaining choice, that also makes sense as per the passage

GMATNinja · Answer

Question 3

The conclusion drawn from recent observations about globular clusters is that  The Milky Way may have formed from the collapse of many clusters into a single galaxy, over a long period of time.  Here's how this conclusion is presented in the structure of the passage:

P1: The Milky Way is formed of many (~125) globular clusters distributed in a halo around the galactic nucleus. This distribution holds vital clues to how the galaxy was formed. 
 P2: Conventional theory says: The Milky Way was formed in a short period of time (~200 million years), from the collapse of a single spherical cloud of gas. This implies that all stars in the halo should be nearly the same age. 
 P3: Bolte has found discrepancies in the age of stars as large at 2 billion years. His findings challenge the conventional theory. 
 P4: Larsons' "renegade" theory explains these discrepancies by arguing that the Milky Way was actually formed from multiple gas clouds. Toomre's models support this theory by suggesting how multiple galaxies could merge into one.

The best answer choice will back up these recent observations of age discrepancies within the galactic halo (wow, I am  so glad  I got to say "galactic halo") or reinforce the "renegade" theory by explaining how multiple galaxies could become one.

Why do we care about the absolute age of the Milky Way as a whole? We're looking for information about the age of stars in the halo. This is irrelevant to the question being asked, so we we'll eliminate (A).

We're only concerned about explaining age discrepancies within the Milky Way galaxy. Knowing the age of clusters in another galaxy altogether (especially if this knowledge doesn't tell us anything about how they fit into the bigger picture for that galaxy) won't help us strengthen or weaken the conclusion we care about, so let's eliminate (B).

Without more information about how these regular patterns result (or don't result) in collisions and the loss of orbital energy, we can't tie this model back to the theory of many galaxies becoming one Milky Way. Let's eliminate (C).

As with choice (C), knowing that there are different  types  of gas doesn't help us bridge the logical gap between many galaxies existing and many galaxies merging. Eliminate (D).

This choice explicitly reinforces the conclusion by telling us that many individual stars  in the halo of the Milky Way  have  wide discrepancies  in age. If true, we've just taken the example of Palomar and multiplied by it by 1,500. This adds a great amount of quantitative support to Bolte's recent findings. It directly attacks the conventional theory by showing exactly how much variance we're seeing in the age of stars in this halo. It's by far the best answer choice, so we'll stick with (E) and move on.

Question 5 
 
In the final paragraph, the author presents "renegade" theories that could explain the large age discrepancies between globular clusters. Larson's theory is that hundreds of small gas clouds, rather than a single gas cloud, formed what we observe today as one galaxy: the Milky Way. Toomre's computer modeling suggests that multiple spiral galaxies could indeed merge into a single galaxy. Larson's work and Toomre's work reinforce each other, because both illustrate the same theoretical statement: Multiple galaxies can become one, over time.

Now that we've clarified the purpose of this paragraph, let's take a closer look at these two choices.

As you know, (D) most closely captures what we've just read. Toomre's models suggest that multiple galaxies could lose enough energy to merge into one. This provides support for the Larson's big-picture theory (multiple gas clouds becoming one system) as well as the specific process at the heart of that theory (losing orbital energy).

The key words here aren't  only  "widely applicable." We also have to decide whether Toomre's work is really  expanding Larson's theory , because we're being asked how Toomre's work is complementing Larson's. We should eliminate (E) if either of these phrases aren't supported by the passage.

Let's recall why the author brought up Larson and Toomre in the first place: Both works suggest that many galaxies (whether worded as "hundreds of small gas clouds" or "closely interacting spiral galaxies") could become one. So the point of modeling spiral galaxies isn't to look at one galaxy and apply observations about it to many different kinds. The point is to illustrate how these multiple galaxies could have merged into a single galaxy.

Toomre's modeling shows how orbital energy plays a role in this merge, but it  does not expand the theory  of "many become one"...nor does it show us other ways that theory can be applied (for instance, to things that aren't galaxies at all). That's why we eliminate (E). It's more about matching the author's reason for bringing up another person's work than it is about matching specific keywords from choice to passage.

I hope this helps you... um, feel like you're surrounded by a galactic halo...?

dan0015 · Answer

In question 6:

The passage contends that the scientist found only one of each type of clusters: one which is 2 million years younger and one which is 2 million years older.

In B we have the word "some". My question is how can we be sure that there are other clusters which are exactly 2 million years younger or older. What if all the others are between this interval? What do I miss?

bM22 · Answer

Hi  dan0015 ,

What's mentioned in the passage is:  "One of the clusters studied by Bolte is 2 billions years older than most other clusters in the galaxy, while another is 2 billion years younger. A colleague of Bolte contends that the cluster called Palomar 12 is 5 billion years younger than most other globular clusters."

The passage  does not  imply that Bolte found only one of each of type of clusters. The implications of above mentioned lines are that one of the clusters studied by Bolte is 2 billions years older than most other clusters in the galaxy and one that he studied is 2billion years younger. It could also imply that there are still some clusters in that galaxy that could differ by at least 4 billion years. This statement is validated by the last line highlighted above, that a colleague of Bolte did find a cluster called that was 5 billion years younger than most other globular clusters.

Thus B is the correct answer for Question 6.

Hope This Helps.
Thanks.

gmatimothy · Answer

Hey  GMATNinja ,

Would you please elaborate on what #5 choice means when it says "theoretical" support? Does it entail support from work (Toomre's modeling) to simulate Larson's theory? Unsure how that modeling can be described as theoretical. Thanks!

GMATNinja · Answer

Question 5

That's a good question about the meaning of "theoretical" support!

Before we dissect that term, however, notice that it's possible to identify (D) as correct even without worrying too much about the exact meaning of the word "theoretical" in this case.

From the passage, we know that Toomre's computer modeling is cited to support Larson's idea about the formation of the Milky Way. The only answer choices that come close to capturing this meaning are (C) and (D). But notice that (C) says Toomre provided "direct astronomical observations." And since Toomre provided a computer model, not "direct astronomical observations," (C) is definitely wrong, which leaves us with (D).

Regarding the word "theoretical": notice that Toomre does not support Larson's idea with actual data or measurements. That is, Toomre does not provide "astronomical observations." Instead, Toomre provides a computer model which suggests that Larson's idea could be correct.

In other words, Toomre's support for Larson is based on a theoretical model, as opposed to actual observations.

I hope that helps!

Anirudh16 · Answer

Hey  GMATNinja ! the option E in 7th question is "indicate that the theories in question are no longer as unconventional as they once seemed"
.. "are no longer as  unconventional " i.e they are conventional now? Can you please help me understand what I am missing here?

KittyDoodles · Answer

Hi Experts,

Please can you help me with QS 2.

I had rejected Option A as Larson states "The halo of the Milky Way formed over a period of a billion or more years as hundreds of small gas clouds drifted about, collided, lost orbital energy, and finally collapsed into a centrally condensed elliptical system"

How can we infer from the above lines that he also states "amount of time it took to form the galaxy" as galaxy and the spherical halo surrounding it is diff.

Thus isn't the comparison between the amount of time it took the spherical halo around the galaxy to form.

Thanks

RonTargetTestPrep · Answer

The question calls for something that Larson's theory and the conventional theory  both EXPLICITLY address , in ways that contradict one another.

If we absolutely must, we can hold the two theories up against each other point-by-point. But this is actually all that the passage says about Larson's theory:
 the halo of the Milky Way formed over a period of a billion or more years as hundreds of small gas clouds drifted about, collided, lost orbital energy, and finally collapsed into a centrally condensed elliptical system

There's not much here. Remember, the correct answer MUST be  explicitly mentioned  for both theories (as that's the only way to know when they contradict each other)—so why not start out by just checking this very brief blurb about Larson's theory for each of the answer choices?

We have Larson's take on this:  over a period of a billion or more years"

Nothing here about this.

All we have is "small gas clouds". No specs about the specific gases in these clouds.

Nothing about globular clusters at all for Larson.

Nope. (The halo degenerated into something shaped like an ellipse, but we're not told anything about the shape of the original halo.)

Oh hey! We're done. Only A gives us anything that's mentioned in those lines about Larson's theory, so we don't even have to bother with the conventional theory.

RonTargetTestPrep · Answer

The Milky Way galaxy   IS   the "halo". This is stated in the first paragraph :
  The Milky Way contains   about 125 globular clusters (compact groups of anywhere from several tens of thousands to perhaps a million stars)   distributed in a roughly spherical halo   around the galactic nucleus

The "halo", in other words, represents the shape of the entire contents of the Milky Way galaxy.

GMATNinja · Answer

Question 7 
 
Yes, the passage suggests that the "renegade" theories are now more conventional than they used to be.

Thinking about the overall flow of the passage, in the second paragraph we learn about an  earlier  "conventional" view. In the third paragraph, we get some evidence that goes  against  this earlier conventional view.

Because the earlier view has been undermined, astronomers are taking a second look at some alternative theories that were considered renegade  in their own time . But with this new evidence, it appears that the theories are not so "renegade" after all -- which is why the author uses the quotation marks.

So, while these theories used to be quite unconventional, they are now more conventional. (E) is the correct answer to question 7.

I hope that helps!

VerbalBot · Answer

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New observations about the age of some globular clusters in our Milky

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