A black hole is a region of spacetime from which gravity prevents anyt

Question

A black hole is a region of spacetime from which gravity prevents anything, including light, from escaping. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that marks the point of no return. The hole is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics. Quantum field theory in curved spacetime predicts that event horizons emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of a stellar mass (the mass of our sun) or greater.

Black holes of stellar mass are expected to form when very massive stars collapse at the end of their life cycle. After a black hole has formed it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may form. There is a general consensus that supermassive black holes exist in the centers of most galaxies.

Despite its invisible interior, the presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as light. Matter falling onto a black hole can form an accretion disk heated by friction, forming some of the brightest objects in the universe. If there are other stars orbiting a large black hole, their orbit can be used to determine its mass and location. These data can be used to exclude possible alternatives (such as neutron stars). In this way, astronomers have identified numerous stellar black hole candidates in binary systems, and established that the core of our Milky Way galaxy contains a supermassive black hole of about 4.3 million solar masses.   1 
 D 
1. Which of the following can be inferred from the passage about larger black holes?

(A) They are more likely to be found in the center of galaxies than elsewhere in the universe
 (B) They are typically formed when neutron stars collapse
 (C) They emit radiation at a higher temperature than do smaller black holes
 (D) They affect the orbit of nearby stars
 (E) They form accretion disks more frequently than do smaller black holes

2 
 C 
2. According to the passage, all of the following would be helpful in discovering new supermassive black holes in the universe except

(A) Observing interactions with matter
(B) Observing interactions with electromagnetic radiation
(C) Observing levels of emitted radiation
(D) Analyzing the orbits of stars
(E) Focusing on the centers of major galaxies

3 
 D 
3. The primary purpose of the passage above is to

(A) Analyze a surprising scientific discovery
(B) Argue that black holes are important to the scientific community
(C) Explain how supermassive black holes are formed
(D) Describe a scientific phenomenon 
(E) Compare two types of black holes

4 
 D 
4. The author points out that a black hole can continue to grow by absorbing mass in order to:

(A) explain how black holes of stellar mass initially form.
(B) explain why supermassive black holes exist in the centers of most galaxies.
(C) provide evidence for why there is a general consensus that supermassive black holes exist.
(D) account for the existence of supermassive black holes.
(E) support the notion that supermassive black holes form only when very massive stars collapse.

5 
 C 
5. The passage suggests that neutron stars

(A) are more common than black holes
(B) are found throughout the Milky Way galaxies
(C) can be confused for black holes
(D) are not as bright as the accretion disk in a black hole
(E) have a visible interior

6 
 A 
6. The author discusses quantum field theory in order to ________________

A. Highlight the difficulty in detecting some black holes
B. More clearly define what constitutes a black body in thermodynamics
C. Better explain why black holes are “black”
D. Help the reader better understand the general theory of relativity
E. Confirm that a black body in thermodynamics is similar to a black hole in space

CrackverbalGMAT · Answer

1.
A - All we know from the passage is this - "There is a general consensus that supermassive black holes exist in  the centers of most galaxies. ". Supermassive blackholes are a subset of larger blackholes. So we cannot infer anything like this about larger blackholes from supermassive blackholes.
B - No such thing is mentioned in the passage. The passage only states that they are formed from very massive stars.
C - We know that this is not true. Radiation temperature is inversely proportional to their mass. Hence, larger black holes emit radiation at lower temperature. Also, note that the argument states that event horizons emit radiation not the black holes themselves. Eliminate C.
D - Correct answer - " If there are other stars orbiting a large black hole, their orbit can be used to determine its mass and location."
E - All we know is this - "Matter falling onto a black hole can form an accretion disk heated by friction". We cannot infer option E from this sentence.

2.
look at these sentences - 
" inferred through its interaction with other matter and with electromagnetic radiation such as light. "
"If there are other stars orbiting a large black hole, their orbit can be used to determine its mass and location."
"There is a general consensus that supermassive black holes exist in the centers of most galaxies."
Only C remains.

3.
A - nowhere is the passage talking about a "discovery" and nowhere does it mention it to be "surprising". It just describes blackholes.
B - nowhere is the importance of blackholes mentioned.
C - this is mentioned only in the 2nd sentence of the 2nd paragraph. Not the main idea.
D - Correct answer. the passage describes blackholes.
E - what two types? and nowhere is there any comparison mentioned.

KS15 · Answer

Got ACD-will be interested to know how D is the answer too the first question. It is nowhere given the blackholes affect the orbit whereas option A is given.

Thanks.

BillyZ · Answer

Solution

For this function style question, you should first locate where the information given in the question stem is discussed and then examine the context around it. The author talks about a black hole continuing to grow by absorbing mass in the 2nd and 3rd sentence of the 2nd paragraph. Looking at the context, you see that the first sentence simply describes how black holes of stellar mass initially form. Then the author uses the fact that these black holes can absorb mass around them to turn into supermassive black holes.

As a result, answer choice (D) is correct – the author uses this fact to account for how black holes of stellar mass can then become supermassive.

For (A), the fact they absorb mass around them has nothing to do with how they initially form – this is a secondary process after a massive star collapses.

For (B), this fact does not explain at all why they are at the centers of most galaxies – it simply explains how they can go from one stellar mass to millions of stellar masses.

Like (B), the general consensus relates to the fact that they are often found at the center of galaxies, and the author does not use this fact to explain why that is true.

(E), like (A), is incorrect because this fact does help explain anything relating to the initial formation of the black hole.

Correct answer is (D).

800Dreamer · Answer

One more question:

The author discusses quantum field theory in order to ________________

a.Highlight the difficulty in detecting some black holes
 b.More clearly define what constitutes a black body in thermodynamics
 c.Better explain why black holes are “black”
 d.Help the reader better understand the general theory of relativity
 e.Confirm that a black body in thermodynamics is similar to a black hole in space

OA  A

deeeuce · Answer

Hi  GMATNinja   VeritasKarishma 
would really appreciate to learn your opinion on answer to Q N. 1. I am not able to comprehend how D is the answer. 
Though I was initially inclined towards A (which I selected) I see how that option compares in the center of galaxies vs elsewhere. However, the mention in the passage (which Veritas prep test explained as the reason for the answer correctness) that "The orbit of nearby stars are being used to trace blackholes" isn't convincing me to infer that black-hole in return affects nearby stars. My reasoning to this is : presence of my car can be used to predict if I am at home - this doesn't tell that I affect the Car.

Can you help me where I am getting wrong.

KarishmaB · Answer

(A) They are more likely to be found in the center of galaxies than elsewhere in the universe

Not correct. 
Passage: "There is a general consensus that supermassive black holes exist in the centers of most galaxies."
So it is likely that the centre of a galaxy has a black hole. But it is NOT more likely that they will be found in the centre of galaxies than elsewhere. Perhaps there is a part of the universe where there are millions of black holes and hence, black holes are more likely to be found there.

(D) They affect the orbit of nearby stars

Passage: If there are other stars orbiting a large black hole, their orbit can be used to determine its mass and location.

Then obviously, there is some impact that the black hole has on the orbit of the stars. If it had no impact and if having the black hole there or not having it there were the same thing for the orbit of the star, we couldn't have determined anything about the black hole from the orbit.
As per your reasoning, your car tells us about your location. You impact the car as in you take it around. So if it is at your office, we know you are at office; if it is at your home, we know you are home. Similarly, properties of the orbit (symmetry, shape) etc could tell us about the properties of the black hole (say a black hole of this size leads to such an orbit etc)

VidyaSV · Answer

Can someone explain the reason for Q6
I thought the author cited the Quantum theory to draw the similarity

ypetrunina · Answer

Hi. I also thought so but later I understood.
 Quantum field theory in curved spacetime predicts that event horizons emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of a stellar mass (the mass of our sun) or greater.

From this text we can understand that the author compares a black body and a black hole, they both emit radiation and have a temperature that helps to detect that radiation. The bigger the mass of a black hole, the less radiation can be observed/seen/detected - see from the text "making it difficult  to observe this radiation  for black holes of a stellar mass"

Therefore the answer for question 6 is A.

tinbq · Answer

Hi  VeritasKarishma ,

I am confused about the question stem, which asks about  Larger  black holes, while the official explanation refers to a detail about  Large  black hole from the passage.
Is the question stem correct? Thanks.

KarishmaB · Answer

Yes, they are referring to the same black holes. 
When the question stem says "larger black holes," it is referring to the black holes that are larger (vs the ones that are smaller).
The passage also talks about "large" black holes that are formed when massive stars collapse.

Both are referring to the same thing.

mahmudul55 · Answer

I have few questions- 
1. How is the option (i) of the 6th question correct?? 
2. If it is correct, then the radiation which emit from the black hole how help to detect the black??

3. making it difficult to observe this radiation for black holes of a stellar mass (the mass of our sun) or greater - this sentence is understanding that low temperature is the main barrier to observe this radition which emit from black hole of biggier mass, is not it??

Posted from my mobile device

Haardy7007 · Answer

In the last statement, aren’t we saying that radiation is difficult to detect? Or is it other way around?

VerbalBot · Answer

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A black hole is a region of spacetime from which gravity prevents anyt

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A black hole is a region of spacetime from which gravity prevents anyt

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