Galaxy clusters are vast groups of galaxies. Extremely hot, thin gas fills the space between galaxies in a cluster, emitting...
GMAT Reading Comprehension : (RC) Questions
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Galaxy clusters are vast groups of galaxies. Extremely hot, thin gas fills the space between galaxies in a cluster, emitting X-rays. Astronomers have calculated that these X-rays carry away so much energy that the gas should cool and settle into the center of the cluster, growing dense enough to form trillions of new stars. But surprisingly, observations have not detected anything like what had been predicted.
In the 1990s, satellite telescopes discovered two huge cavities or "bubbles" in the hot gas in the center of the Perseus cluster, filled with magnetic fields and energetic particles. These energetic bubbles are expanding and pushing aside the hot gas. Similar bubbles were soon found in several other clusters. Measurements showed that in clusters containing such bubbles, the hot intergalactic gas is not cooling and settling, which suggests that the bubbles keep the gas from forming new stars.
Only one kind of object known to science could generate enough energy to produce these bubbles: a supermassive black hole. A black hole is a kind of gravitational sinkhole that sucks in matter—such as gas—and energy. But the energy the black hole devours also causes it to rotate. The rotation twists the fabric of space around the black hole, catapulting out some of the inflowing gas in two opposing jets. The faster the black hole spins, the greater a proportion of the incoming gas is ejected in these jets.
Each galaxy cluster centers on one especially large galaxy containing a huge black hole. In the Perseus cluster, the two vast bubbles in the hot intergalactic gas are aligned with jets of energy emanating from the middle of the large central galaxy. Thus, this galaxy's black hole must be producing the bubbles.
This may be part of a cyclical process, since not all galaxy clusters show such bubbles. As a cluster's gas cools, it falls into the central black hole, making it shoot out jets of energy. These jets create bubbles that heat the gas, diminishing its inflow. With less incoming gas, the black hole spins more slowly, so the energy jets and bubbles dwindle, letting the hot gas cool again to repeat the cycle.
Ques. 1/4
According to the passage, in the Perseus cluster
Solution
1. Passage Analysis:
Progressive Passage Analysis
| Text from Passage | Analysis |
|---|---|
| Galaxy clusters are vast groups of galaxies. | What it says: Groups of galaxies exist, and they're really big What it does: Basic definition to orient readers Source/Type: Basic scientific fact Connection to Previous Sentences: First sentence - establishes our main topic Visualization: Imagine 1,000+ individual galaxies grouped together in space Reading Strategy Insight: Simple opening - author is easing us into the topic |
| Extremely hot, thin gas fills the space between galaxies in a cluster, emitting X-rays. | What it says: Between those galaxies is very hot gas that gives off X-rays What it does: Adds one key detail about what's IN galaxy clusters Source/Type: Observable scientific fact Connection to Previous Sentences: This builds on sentence 1 by describing what exists between the galaxies mentioned Visualization: Think of 1,000 galaxies with superhot, invisible gas filling all the empty space, glowing with X-ray energy Reading Strategy Insight: Still building foundation - adding one detail at a time |
| Astronomers have calculated that these X-rays carry away so much energy that the gas should cool and settle into the center of the cluster, growing dense enough to form trillions of new stars. | What it says: Scientists expected: gas loses energy → gas cools → gas moves to center → gas forms lots of new stars What it does: Sets up scientific expectation/prediction Source/Type: Astronomers' theoretical prediction Connection to Previous Sentences: This builds on the X-ray gas from sentence 2, explaining what scientists thought should happen to that gas Visualization: Expected process: Hot gas (3,000°F) → Cooled gas (1,000°F) → Dense center → 5 trillion new stars forming Reading Strategy Insight: Setting up "what should happen" - usually means we're about to learn what actually happens instead |
| But surprisingly, observations have not detected anything like what had been predicted. | What it says: Reality doesn't match the prediction from sentence 3 What it does: Creates the central puzzle/mystery Source/Type: Observational evidence Connection to Previous Sentences: This directly contrasts with sentence 3's prediction. The "But" signals we're getting the real story now Visualization: Expected: 5 trillion new stars forming Reality: Close to 0 new stars detected Reading Strategy Insight: This is the central mystery the passage will solve - not new complexity, but the main question! |
| In the 1990s, satellite telescopes discovered two huge cavities or "bubbles" in the hot gas in the center of the Perseus cluster, filled with magnetic fields and energetic particles. | What it says: Scientists found two giant empty spaces (bubbles) in the hot gas, containing magnetic fields and energetic particles What it does: Introduces the first clue to solving the mystery Source/Type: Observational discovery (1990s satellites) Connection to Previous Sentences: This provides evidence about WHY the prediction failed - something is creating bubbles in the gas Visualization: In the Perseus cluster's hot gas center: 2 enormous bubble-shaped empty spaces, each filled with magnetic energy Reading Strategy Insight: Feel relieved - we're getting answers now, not more problems! |
| These energetic bubbles are expanding and pushing aside the hot gas. | What it says: The bubbles are growing bigger and shoving the hot gas out of the way What it does: Explains what the bubbles DO - provides mechanism Source/Type: Observational description Connection to Previous Sentences: This builds directly on sentence 5's bubble discovery, explaining their action. This helps explain why stars aren't forming - the gas is being pushed around! Visualization: Two expanding bubbles physically shoving hot gas away from cluster center where stars would form Reading Strategy Insight: The mystery is becoming clearer - bubbles disrupt star formation |
| Similar bubbles were soon found in several other clusters. | What it says: This bubble phenomenon happens in multiple galaxy clusters, not just Perseus What it does: Shows the pattern is widespread Source/Type: Extended observational evidence Connection to Previous Sentences: This reinforces that the bubbles from sentences 5-6 represent a general pattern, not a one-time oddity Visualization: Perseus cluster + 5-10 other galaxy clusters, all showing similar bubble patterns Reading Strategy Insight: This strengthens the case - when something happens repeatedly, it suggests a systematic cause |
| Measurements showed that in clusters containing such bubbles, the hot intergalactic gas is not cooling and settling, which suggests that the bubbles keep the gas from forming new stars. | What it says: In clusters with bubbles: gas doesn't cool → gas doesn't settle → no new stars form. The bubbles prevent star formation. What it does: Directly connects bubbles to the original mystery - this is the answer! Source/Type: Scientific measurements and interpretation Connection to Previous Sentences: This SOLVES the mystery from sentence 4! Bubbles (sentences 5-7) explain why predictions failed (sentences 3-4) Visualization: Clusters WITH bubbles: Gas stays hot → No settling → 0 new stars Clusters WITHOUT bubbles: Gas cools → Settles → Trillions of stars Reading Strategy Insight: Major relief point - the central puzzle is solved! Bubbles = reason for no star formation |
| Only one kind of object known to science could generate enough energy to produce these bubbles: a supermassive black hole. | What it says: Only supermassive black holes have enough power to create these bubbles What it does: Identifies the source/cause of the bubbles Source/Type: Scientific deduction based on energy requirements Connection to Previous Sentences: This goes one step deeper - we know bubbles prevent star formation (sentence 8), now we know what creates the bubbles Visualization: Energy required for bubbles: Enormous Objects capable of this energy: Only supermassive black holes Reading Strategy Insight: We're building a complete chain: Black holes → Bubbles → No star formation What We Know So Far: Galaxy clusters should form stars, but don't because bubbles disrupt the gas, and only black holes can make these bubbles |
| A black hole is a kind of gravitational sinkhole that sucks in matter—such as gas—and energy. | What it says: Simple explanation: Black holes are like drains that pull in gas and energy What it does: Provides basic definition for readers unfamiliar with black holes Source/Type: Educational explanation Connection to Previous Sentences: This helps readers understand the "supermassive black holes" mentioned in sentence 9 - the author is being helpful! Visualization: Black hole like a cosmic vacuum cleaner, sucking in surrounding gas and energy Reading Strategy Insight: Feel relieved here - this is simplification, not new complexity. The author is helping you understand. |
| But the energy the black hole devours also causes it to rotate. | What it says: When black holes consume energy, this makes them spin What it does: Explains what happens inside black holes when they "eat" Source/Type: Scientific mechanism Connection to Previous Sentences: This builds on sentence 10's "sucking in energy" by explaining the consequence - rotation Visualization: Black hole eating gas and energy → Black hole spinning like a top Reading Strategy Insight: We're learning HOW black holes work to understand HOW they make bubbles |
| The rotation twists the fabric of space around the black hole, catapulting out some of the inflowing gas in two opposing jets. | What it says: The spinning warps space and shoots out gas in two opposite directions What it does: Explains the mechanism that creates the jets Source/Type: Scientific explanation of physics Connection to Previous Sentences: This continues the chain: sucking in gas (sentence 10) → rotation (sentence 11) → space warping → jets shooting out Visualization: Spinning black hole warps space like a twisted towel, launching gas jets in opposite directions (north and south) Reading Strategy Insight: We're getting close to understanding how jets create the bubbles we learned about earlier! |
| The faster the black hole spins, the greater a proportion of the incoming gas is ejected in these jets. | What it says: Faster spinning = more gas shot out in jets What it does: Shows the relationship between spin speed and jet power Source/Type: Scientific relationship/principle Connection to Previous Sentences: This elaborates on the jet mechanism from sentence 12, giving us the "control knob" - spin speed determines jet strength Visualization: Slow spin: 20% of gas ejected in jets Fast spin: 80% of gas ejected in jets Reading Strategy Insight: This detail will be important later - spin speed controls the whole process |
| Each galaxy cluster centers on one especially large galaxy containing a huge black hole. | What it says: Every galaxy cluster has one big central galaxy with a supermassive black hole What it does: Connects black holes back to galaxy clusters - the topics are merging! Source/Type: Observational fact about cluster structure Connection to Previous Sentences: This brings us back to galaxy clusters (sentences 1-8) after learning about black hole mechanics (sentences 9-13) Visualization: Galaxy cluster with 1,000 galaxies → 1 central big galaxy → 1 supermassive black hole at center Reading Strategy Insight: We're connecting the dots - clusters have black holes, and we know black holes make jets! |
| In the Perseus cluster, the two vast bubbles in the hot intergalactic gas are aligned with jets of energy emanating from the middle of the large central galaxy. | What it says: In Perseus, the bubbles line up perfectly with energy jets coming from the central galaxy's black hole What it does: Provides direct observational evidence connecting jets to bubbles Source/Type: Specific observational evidence Connection to Previous Sentences: This connects bubbles (sentence 5) with jets (sentences 12-13) using Perseus as the example Visualization: Perseus cluster center: Central galaxy with black hole → 2 jets shooting north/south → 2 bubbles positioned exactly north/south of center Reading Strategy Insight: Smoking gun evidence! The alignment proves jets create bubbles |
| Thus, this galaxy's black hole must be producing the bubbles. | What it says: Therefore, the black hole is definitely creating the bubbles What it does: States the logical conclusion - this is a restatement for clarity Source/Type: Author's logical conclusion Connection to Previous Sentences: This restates what we could conclude from sentence 15's evidence. The "Thus" signals: here's the obvious conclusion Visualization: Black hole → Jets → Bubbles (confirmed causal chain) Reading Strategy Insight: Feel confident here - this is NOT new information! The author is helping by stating the clear conclusion. What We Know So Far: Complete chain established - Black holes create jets that create bubbles that prevent star formation |
| This may be part of a cyclical process, since not all galaxy clusters show such bubbles. | What it says: This might be a repeating cycle because some clusters have bubbles and others don't What it does: Introduces the idea that this is a cycle, not a permanent state Source/Type: Author's hypothesis based on varying observations Connection to Previous Sentences: This explains why bubbles aren't found in ALL clusters (contrasting with sentence 7's "several other clusters") - suggests an on/off cycle Visualization: 10 galaxy clusters observed: 4 have bubbles currently, 6 don't have bubbles currently Reading Strategy Insight: We're moving from "what happens" to "when does it happen" - adding timing element |
| As a cluster's gas cools, it falls into the central black hole, making it shoot out jets of energy. | What it says: Step 1 of cycle: Cool gas falls into black hole → black hole shoots out jets What it does: Describes the beginning of the cycle Source/Type: Author's explanation of cyclical mechanism Connection to Previous Sentences: This builds on the cyclical idea from sentence 17, giving the first step. Uses black hole jet mechanism from sentences 10-13 Visualization: Cycle begins: Cool gas (1,000°F) flows into central black hole → Black hole spins faster → Jets shoot out Reading Strategy Insight: This reuses concepts we already learned - no new complexity! |
| These jets create bubbles that heat the gas, diminishing its inflow. | What it says: Step 2 of cycle: Jets make bubbles → bubbles heat up the gas → less gas flows toward black hole What it does: Continues the cycle explanation Source/Type: Author's explanation of cyclical mechanism Connection to Previous Sentences: This continues from sentence 18's jets, using bubble mechanisms from sentences 6-8 Visualization: Jets create bubbles → Bubbles heat gas back up to 3,000°F → Hot gas stops flowing toward center Reading Strategy Insight: Still reusing familiar concepts - jets, bubbles, gas heating |
| With less incoming gas, the black hole spins more slowly, so the energy jets and bubbles dwindle, letting the hot gas cool again to repeat the cycle. | What it says: Step 3: Less gas → black hole slows down → weaker jets → smaller bubbles → gas cools → cycle starts over What it does: Completes the cycle and shows how it repeats Source/Type: Author's explanation of cyclical mechanism Connection to Previous Sentences: This completes the cycle started in sentences 18-19, using the spin-speed principle from sentence 13, and returns to the cooling gas from sentence 18 Visualization: Complete cycle: Cool gas (1,000°F) → Black hole spins fast → Strong jets → Big bubbles → Hot gas (3,000°F) → Less inflow → Black hole slows → Weak jets → Small bubbles → Gas cools to 1,000°F → REPEAT Reading Strategy Insight: Major satisfaction point - we now understand the complete system! Everything connects back to concepts we learned earlier. Final Summary: We solved the original mystery (why no star formation) and learned it's part of a repeating cycle controlled by black holes. |
2. Passage Summary:
Author's Purpose:
To explain how a scientific mystery was solved by showing how supermassive black holes prevent star formation in galaxy clusters through a cyclical process.
Summary of Passage Structure:
In this passage, the author walks us through the discovery and solution of a major astronomical puzzle:
- First, the author sets up the mystery by explaining what scientists expected to happen in galaxy clusters (lots of new stars forming) versus what they actually observed (almost no new stars).
- Next, the author introduces the key clue that solved the mystery - the discovery of giant "bubbles" in the hot gas of galaxy clusters that were pushing the gas around and preventing star formation.
- Then, the author explains what creates these bubbles by describing how supermassive black holes work - how they spin, shoot out jets of energy, and create the bubbles that disrupt star formation.
- Finally, the author shows that this is not a one-time event but part of a repeating cycle where black holes alternately heat and cool the gas in galaxy clusters over long periods of time.
Main Point:
Supermassive black holes at the centers of galaxy clusters create a cyclical heating and cooling process that prevents the massive star formation that scientists originally expected to see, solving a major puzzle in astronomy.
3. Question Analysis:
The question asks us to identify what is true about the Perseus cluster specifically, according to the passage. This is a detail question that requires us to find specific information about Perseus rather than general information about galaxy clusters.
Connecting to Our Passage Analysis:
From our passage analysis, we learned that Perseus cluster is mentioned in several key places:
- It's where the first bubbles were discovered in the 1990s (sentence 5)
- It's used as the primary example to show the connection between black holes and bubbles (sentence 15)
- The passage establishes that in clusters with bubbles, "the hot intergalactic gas is not cooling and settling" (sentence 8)
- Perseus is specifically described as having these bubbles that prevent star formation
The passage analysis shows that Perseus cluster serves as the main case study for demonstrating how supermassive black holes create bubbles that disrupt the normal cooling process of intergalactic gas.
Prethinking:
Based on our analysis, Perseus cluster is described as having the bubbles that prevent gas from cooling and forming stars. The passage specifically states that "in clusters containing such bubbles, the hot intergalactic gas is not cooling and settling." Since Perseus definitely contains these bubbles, this should directly apply to Perseus cluster.
Answer Choices Explained
A
the energy jets from the central black hole are dwindling
Why It's Wrong:
• The passage doesn't describe Perseus as currently having dwindling energy jets
• Perseus is used as an example of active bubble formation, suggesting strong jets
• The cyclical process described shows jets dwindle in the final stage, but Perseus isn't said to be in this stage
Common Student Mistakes:
1. Did I confuse the cyclical process description with Perseus's current state?
→ The final sentences describe a general cycle, not Perseus specifically
1. Am I mixing up what happens in different stages of the cycle?
→ Focus on what the passage directly states about Perseus, not the theoretical cycle
• The passage doesn't describe Perseus as currently having dwindling energy jets
• Perseus is used as an example of active bubble formation, suggesting strong jets
• The cyclical process described shows jets dwindle in the final stage, but Perseus isn't said to be in this stage
Common Student Mistakes:
1. Did I confuse the cyclical process description with Perseus's current state?
→ The final sentences describe a general cycle, not Perseus specifically
1. Am I mixing up what happens in different stages of the cycle?
→ Focus on what the passage directly states about Perseus, not the theoretical cycle
B
the hot intergalactic gas is not continuously cooling
Why It's Right:
• The passage explicitly states that "in clusters containing such bubbles, the hot intergalactic gas is not cooling and settling"
• Perseus cluster is clearly identified as containing these bubbles
• This directly connects Perseus to the disrupted cooling process
• The bubbles prevent the continuous cooling that would lead to star formation
Key Evidence: "Measurements showed that in clusters containing such bubbles, the hot intergalactic gas is not cooling and settling, which suggests that the bubbles keep the gas from forming new stars."
• The passage explicitly states that "in clusters containing such bubbles, the hot intergalactic gas is not cooling and settling"
• Perseus cluster is clearly identified as containing these bubbles
• This directly connects Perseus to the disrupted cooling process
• The bubbles prevent the continuous cooling that would lead to star formation
Key Evidence: "Measurements showed that in clusters containing such bubbles, the hot intergalactic gas is not cooling and settling, which suggests that the bubbles keep the gas from forming new stars."
C
intergalactic gas is growing dense enough to form new stars
Why It's Wrong:
• This contradicts the main point of the passage
• The passage establishes that Perseus has bubbles that prevent star formation
• The original mystery was that star formation wasn't happening as predicted
Common Student Mistakes:
1. Did I confuse what scientists predicted with what actually happens?
→ Scientists predicted star formation, but observations showed it's not happening
1. Am I reading about the wrong type of cluster?
→ Perseus specifically has bubbles that prevent star formation
• This contradicts the main point of the passage
• The passage establishes that Perseus has bubbles that prevent star formation
• The original mystery was that star formation wasn't happening as predicted
Common Student Mistakes:
1. Did I confuse what scientists predicted with what actually happens?
→ Scientists predicted star formation, but observations showed it's not happening
1. Am I reading about the wrong type of cluster?
→ Perseus specifically has bubbles that prevent star formation
D
two huge, central black holes are filled with magnetic fields and energetic particles
Why It's Wrong:
• Perseus has one central galaxy with one supermassive black hole, not two
• The bubbles contain magnetic fields and energetic particles, not the black holes
• This misrepresents the passage's description of cluster structure
Common Student Mistakes:
1. Did I confuse the number of bubbles with the number of black holes?
→ Two bubbles exist, but they're created by one central black hole
1. Did I misread what contains the magnetic fields?
→ The bubbles contain magnetic fields, not the black holes themselves
• Perseus has one central galaxy with one supermassive black hole, not two
• The bubbles contain magnetic fields and energetic particles, not the black holes
• This misrepresents the passage's description of cluster structure
Common Student Mistakes:
1. Did I confuse the number of bubbles with the number of black holes?
→ Two bubbles exist, but they're created by one central black hole
1. Did I misread what contains the magnetic fields?
→ The bubbles contain magnetic fields, not the black holes themselves
E
bubbles in the hot intergalactic gas are causing a supermassive black hole to spin rapidly
Why It's Wrong:
• This reverses the cause-and-effect relationship
• Black holes create bubbles through jets, not the other way around
• The passage shows bubbles are the result of black hole activity, not the cause
Common Student Mistakes:
1. Did I mix up the direction of causation?
→ Black holes (cause) create jets that create bubbles (effect)
1. Am I confusing the cyclical feedback with the basic mechanism?
→ While there's a cycle, the fundamental relationship is black holes creating bubbles
• This reverses the cause-and-effect relationship
• Black holes create bubbles through jets, not the other way around
• The passage shows bubbles are the result of black hole activity, not the cause
Common Student Mistakes:
1. Did I mix up the direction of causation?
→ Black holes (cause) create jets that create bubbles (effect)
1. Am I confusing the cyclical feedback with the basic mechanism?
→ While there's a cycle, the fundamental relationship is black holes creating bubbles
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