Many stars in our galaxy reside in open clustersgroups of a few dozen

Question

Many stars in our galaxy reside in open clusters—groups of a few dozen to a few thousand stars sharing a common origin. These clusters are relatively young, making them prime targets for studying how planetary systems form and evolve. Recent surveys reveal that several open clusters host exoplanets, raising intriguing questions about whether crowded stellar neighborhoods influence the types of planets that can develop.

A prominent case is the system K2-25, discovered by Johnson and colleagues while analyzing data from a space-based observatory. K2-25 is an M-dwarf star in the Hyades cluster, located about 150 light-years away, and it hosts a Neptune-sized planet orbiting remarkably close to its star. Because M-dwarfs are smaller and cooler than the sun, detecting a sizable planet in such a tight orbit came as a surprise to many researchers.

One puzzle is the relatively high metallicity—elements heavier than helium—observed in both K2-25 and other cluster stars. Historically, stars closer to the galactic center tend to display higher metallicities, while more distant stars are generally poorer in these elements. Yet the Hyades appears enriched beyond earlier expectations. Some theorize that interactions within the dense cluster environment may have boosted heavier element retention, thus facilitating the rapid formation of planets like K2-25 b.

Another piece of evidence comes from orbital oddities. The planet’s short period and potentially tilted orbit suggest that close encounters with other cluster members could have altered its path. In a more isolated setting, random stellar flybys would be far less frequent, making such orbital dynamics improbable. This highlights how clustering can shape not just planet formation but also the subsequent evolution of planetary orbits.

Future investigations aim to pinpoint additional cluster exoplanets with peculiar characteristics, allowing astronomers to compare multiple systems in different clusters. By analyzing metallicities, orbital configurations, and stellar ages, scientists hope to determine whether such environments commonly produce planets unlike those formed around more solitary stars. If ongoing surveys reveal a pattern, it would strengthen the notion that a star’s birthplace—especially if it belongs to a densely populated cluster—profoundly influences both the emergence and the fate of its planetary companions.    1 
 1. It can be inferred from the passage that if the hypothesis regarding cluster-based exoplanet formation is correct, then exoplanetary systems within open clusters could likely

A. retain lower levels of heavy elements than stars in isolated regions
B. evidence abnormal orbital patterns driven by more frequent star encounters
C. fail to develop large gaseous planets because of the higher likelihood of orbital disruptions
D. contain relatively higher levels of helium than stars closer to the galactic center
E. feature irregular planetary rotation influenced by multiple stellar flybys in the cluster

2 
 2. To support the claim that dense cluster environments may enhance the retention of heavy elements in stars, the passage mentions that

A. exoplanets in open clusters are typically larger than those around isolated stars
B. K2-25 hosts a Neptune-sized planet in an unexpected tight orbit
C. M-dwarf stars are less likely to form planets in crowded environments
D. the Hyades cluster shows higher metallicity than expected for its location in the galaxy
E. the internal dynamics of open clusters prevent heavy elements from being lost

3 
 3. The passage uses the example of K2-25 b to suggest that

A. Stars in the Hyades cluster have relatively high metallicity
B. Planets orbiting starts in close clusters can have regular orbits
C. Planets can develop close to stars
D. Heavy element retention can boost the rapid formation of certain planets close to host stars
E. Stars in our galaxy can reside in open clusters

4 
 4. The main purpose of the passage is to

A. argue that all exoplanets in open clusters have unusually high metallicity
B. present evidence that dense stellar environments influence the formation and orbital characteristics of planetary systems
C. describe the discovery and specific features of the K2-25 system
D. explain why open clusters are less likely to retain heavy elements compared to isolated stars
E. assess the impact of a star's birthplace on the distribution of heavy elements in the galaxy

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Bunuel · Answer

Official Solution:

1. It can be inferred from the passage that if the hypothesis regarding cluster-based exoplanet formation is correct, then exoplanetary systems within open clusters could likely

A. retain lower levels of heavy elements than stars in isolated regions
B. evidence abnormal orbital patterns driven by more frequent star encounters
C. fail to develop large gaseous planets because of the higher likelihood of orbital disruptions
D. contain relatively higher levels of helium than stars closer to the galactic center
E. feature irregular planetary rotation influenced by multiple stellar flybys in the cluster

A) Incorrect:  The passage suggests cluster stars may have  higher  heavy-element content, not lower, possibly due to dense environments retaining more metals.

B) Correct:  The text discusses how K2-25’s orbit might be shaped by repeated gravitational interactions in a crowded cluster, implying abnormal orbital patterns.

C) Incorrect:  The passage does not assert that large gas planets  cannot  form; K2-25 b is already an example of a Neptune-sized planet in a cluster.

D) Incorrect:  The passage does not addresses helium content in cluster stars, focusing instead on metals such as iron and nickel. Therefore, there is no support for suggesting increased helium levels.

E) Incorrect:  The passage highlights  orbital  distortions rather than specifically altered  rotational  periods of planets.

2. To support the claim that dense cluster environments may enhance the retention of heavy elements in stars, the passage mentions that

A. exoplanets in open clusters are typically larger than those around isolated stars
B. K2-25 hosts a Neptune-sized planet in an unexpected tight orbit
C. M-dwarf stars are less likely to form planets in crowded environments
D. the Hyades cluster shows higher metallicity than expected for its location in the galaxy
E. the internal dynamics of open clusters prevent heavy elements from being lost

A) Incorrect:  The passage discusses the size of exoplanets like K2-25 b but does not generalize that exoplanets in open clusters are typically larger than those around isolated stars. This option misrepresents the information by making an unsupported broad claim.

B) Incorrect:  While the passage highlights that K2-25 hosts a Neptune-sized planet in a tight orbit, this point is used to illustrate how stellar encounters can affect planetary orbits rather than directly supporting the retention of heavy elements in stars.

C) Incorrect:  The passage actually provides evidence that M-dwarf stars in clusters can host sizable planets, which contradicts the idea that they are less likely to form planets in crowded environments. This option misinterprets the passage's content.

D) Correct:  The passage specifically mentions that the Hyades cluster appears enriched in heavy elements beyond earlier expectations. This higher metallicity suggests that dense cluster environments may help retain heavy elements, thereby supporting the claim.

E) Incorrect:  While the passage discusses how the internal dynamics of open clusters can influence planetary orbits through stellar encounters, it does not state that these dynamics prevent heavy elements from being lost. This option introduces information not covered in the passage.

3. The passage uses the example of K2-25 b to suggest that

A. Stars in the Hyades cluster have relatively high metallicity
B. Planets orbiting starts in close clusters can have regular orbits
C. Planets can develop close to stars
D. Heavy element retention can boost the rapid formation of certain planets close to host stars
E. Stars in our galaxy can reside in open clusters

A) Incorrect:  While the passage mentions higher metallicity in the Hyades cluster, the specific use of K2-25 b primarily illustrates the influence of cluster environments on planetary orbits rather than focusing solely on metallicity.

B) Incorrect:  The passage actually suggests that planetary orbits in dense clusters may become unusual or altered due to frequent stellar interactions, not necessarily regular.

C) Incorrect:  Although K2-25 b is a Neptune-sized planet close to its star, the passage emphasizes how its close orbit may result from stellar interactions within the cluster, not merely the development of close-in planets.

D) Correct:  The example of K2-25 b, with its close and potentially tilted orbit, supports the idea that the retention of heavier elements in dense cluster environments can facilitate the rapid formation and stabilization of planets near their host stars.

E) Incorrect:  While true, this statement is a general fact about stars and open clusters and does not specifically relate to the use of K2-25 b as an example in the passage.

4. The main purpose of the passage is to

A. argue that all exoplanets in open clusters have unusually high metallicity
B. present evidence that dense stellar environments influence the formation and orbital characteristics of planetary systems
C. describe the discovery and specific features of the K2-25 system
D. explain why open clusters are less likely to retain heavy elements compared to isolated stars
E. assess the impact of a star's birthplace on the distribution of heavy elements in the galaxy

A) Incorrect:  The passage discusses that several open clusters, including the Hyades, have stars with high metallicity, but it does not argue that  all  exoplanets in open clusters have unusually high metallicity. This option overgeneralizes the information presented.

B) Correct:  The passage provides multiple lines of evidence—such as the high metallicity in cluster stars, the peculiar orbits of exoplanets like K2-25 b, and the influence of frequent stellar encounters—to support the idea that dense stellar environments significantly affect both the formation and the orbital dynamics of planetary systems.

C) Incorrect:  While the K2-25 system is used as a prominent example, the passage's main focus is broader, encompassing how open clusters as environments influence planetary systems in general, not solely describing the discovery and features of K2-25.

D) Incorrect:  On the contrary, the passage suggests that dense cluster environments may enhance the retention of heavy elements, facilitating planet formation. This option misrepresents the passage by stating the opposite.

E) Incorrect:  The passage does mention heavy elements and their retention within clusters but does not assess the impact of a star's birthplace.

AshishK0721 · Answer

What is the right way to approach a passage like this? I couldn't understand much on my first read and I always struggle with passages of this type. Got just 1/4 right.

bb · Answer

My recommendation would be the same for all passages - do not rush to read them and adjust the speed as you go. If it is dense and hard, slow down a bit but still use the same strategy of reading every word, but also reading for intent, and purpose rather than just meaning. Why is the author putting this here. Is this an example or is this a contradiction or is this the main point?

Many stars in our galaxy reside in open clustersgroups of a few dozen

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GMAT Reading Comprehension (RC) Questions

Many stars in our galaxy reside in open clustersgroups of a few dozen

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

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Perfect 805 Score Debrief by Julia

My Rewards