Stars create energy through the process of fusion. When a star explode

Question

Stars create energy through the process of fusion. When a star explodes—a phenomenon called a supernova—so much energy is released that heavy metals such as iron and gold are formed, seeding surrounding hydrogen clouds. Newer stars therefore contain more heavy elements in their atmospheres. Heavy elements form the materials that make up our planet (and even human bodies). It is believed that for a system of planets such as our solar system to form around a star during cloud contraction, the presence of these heavy elements in the cloud is a necessity.

A molecular cloud can become unstable and collapse by the force of gravity, overcoming outward thermal pressure of the constituent gases. At a given temperature and density, two critical measures of size, Jeans mass and Jeans length, can be calculated. If the size of the cloud exceeds either of these critical values, gravity will ultimately win, and the probability of eventual cloud contraction is high. However, some outside influence is still evidently required for a theoretically unstable cloud to initiate collapse. The natural rotation of a galaxy can slowly alter the structure of a cloud, for instance. Surrounding supernovae can generate shockwaves powerful enough to affect the debris in other clouds, forcing the debris inward and possibly causing contraction to begin. One theory states that density waves propagating through spiral structures can also sufficiently stimulate clouds to cause contraction.    1 
 Consider each of the answer choices separately and indicate all that apply. 
 1. The author of the passage suggests that cloud contraction may begin in which of the following ways?

A. Through the process of fusion
B. Explosions of stars within a close enough proximity, generating shockwaves that prompt contraction in nearby clouds
C. Debris forced outwards from a cloud

2  
 2. Which of the following inferences about our solar system is best supported by the passage?

(A) Life in the solar system depends on energy from the sun.
(B) When the system reaches a particular size, it can become unstable and begin to collapse.
(C) The natural rotation of the galaxy can alter the galaxy’s structure.
(D) It is believed to have been formed from materials “seeded” into hydrogen clouds.
(E) It produced so much energy when it was formed that heavy elements were generated.

3  
 3. It can be inferred from the passage that which of the following inhibits interstellar cloud collapse?

(A) Supernova explosions
(B) Galactic rotation
(C) Thermal pressure
(D) Gravitational force
(E) Density waves

Sajjad1994 · Answer

OE

1. The author of the passage suggests that cloud contraction may begin in which of the following ways?

In the third paragraph,  “The natural rotation of a galaxy,” “surrounding supernovae,”  and  “density waves”  are listed as examples of the outside influence  “evidently required for a theoretically unstable cloud to initiate collapse.”  The first statement is a trap—fusion appears in the first paragraph and the author does not suggest that it leads to cloud contraction. (While the passage does suggest that fusion is related to supernovae and that supernovae can contribute to cloud collapse, don’t fill in the gaps yourself—the passage simply does not provide enough information to infer that fusion is part of a series of events that begins cloud contraction.) The second statement is true (realizing this requires you to match up  “explosions of stars”  in the answer choice with  “supernovae”  in the third paragraph). The third statement is a distortion—forcing debris inward, not outward, may cause cloud contraction to begin.

Answer: B

Sajjad1994 · Answer

OE

2. Which of the following inferences about our solar system is best supported by the passage?

Choice (A)  is true in real life, of course, but is not mentioned in the passage.

Choice (B)  refers to the molecular clouds in the second paragraph, not to our solar system.

Choice (C)  is reminiscent of this sentence in the third paragraph— “The natural rotation of a galaxy can slowly alter the structure of a cloud” —but this does not refer to our solar system. Found in the first paragraph, correct answer  (D)  reflects that  “for a system of planets such as our solar system to form around a star during cloud contraction, the presence of these heavy elements in the cloud is a necessity.”  The first paragraph additionally states that  “heavy metals such as iron and gold are formed, seeding surrounding hydrogen clouds.”

Choice (E)  gets the story backwards—heavy elements were needed to create the solar system, not vice-versa. 
  
  Answer: D

Sajjad1994 · Answer

OE

3. It can be inferred from the passage tha

The second paragraph states that “outward thermal pressure of the constituent gases [of the molecular cloud]” is what is “overcome” in the process of the collapse of the cloud. This is something that “inhibits,” or holds back, cloud collapse. Thus, (C) is correct.

Answer: C

Stars create energy through the process of fusion. When a star explode

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