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# Until recently astronomers have been puzzled by the fate of red giant

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Until recently astronomers have been puzzled by the fate of red giant  [#permalink]

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Updated on: 14 Oct 2019, 03:55
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Until recently astronomers have been puzzled by the fate of red giant and supergiant stars. When the core of a giant star whose mass surpasses 1.4 times the present mass of our Sun ($$M \odot$$) exhausts its nuclear fuel, it is unable to support its own weight and collapses into a tiny neutron star. The gravitational energy released during this implosion of the core blows off the remainder of the star in a gigantic explosion, or a supernova. Since around 50 percent of all stars are believed to begin their lives with masses greater than 1.4 $$M \odot$$ we might expect that one out of every two stars would die as a supernova. But in fact, only one star in thirty dies such a violent death. The rest expire much more peacefully as planetary nebulas. Apparently most massive stars manage to lose sufficient material that their masses drop below the critical value of 1.4 $$M \odot$$ before they exhaust their nuclear fuel.

Evidence supporting this view comes from observations of IRC + 10216, a pulsating giant star located 700 light-years away from Earth. A huge rate of mass loss (One $$M \odot$$ every 10,000 years) has been deduced from infrared observations of ammonia ($$NH_3$$) molecules located in the circumstellar cloud around IRC + 10216. Recent microwave observations of carbon monoxide $$(CO)$$ molecules indicate a similar rate of mass loss and demonstrate that the escaping material extends outward from the star for a distance of at least one light-year. Because we know the size of the cloud around IRC + 10216 and can use our observations of either $$NH_3$$ or CO to measure the outflow velocity, we can calculate an age for the circumstellar cloud. IRC + 10216 has apparently expelled, in the form of molecules and dust grains, a mass equal to that of our entire Sun within the past ten thousand years. This implies that some stars can shed huge amounts of the matter very quickly and thus may never expire as supernovas. Theoretical models, as well as statistics on supernovas and planetary nebulas, suggest that stars that begin their lives with masses around 6 $$M \odot$$ shed sufficient material to drop below the critical value of 1.4 $$M \odot$$. IRC + 10216, for example, should do this in a mere 50,000 years from its birth, only an instant in the life of a star.

But what place does IRC + 10216 have in stellar evolution? Astronomers suggest that stars like IRC + 10216 are actually "protoplanetary nebulas"—old giant stars whose dense cores have almost but not quite rid themselves of the fluffy envelopes of gas around them. Once the star has lost the entire envelope, its exposed core becomes the central star of the planetary nebula and heats and ionizes the last vestiges of the envelope as it flows away into space. This configuration is a full-fledged planetary nebula, long familiar to optical astronomers.
The primary purpose of the passage is to

(A) offer a method of calculating the age of circumstellar clouds
(B) describe the conditions that result in a star's expiring as a supernova
(C) discuss new evidence concerning the composition of planetary nebulas
(D) explain why fewer stars than predicted expire supernovas
(E) survey conflicting theories concerning the composition of circumstellar clouds

Spoiler: :: OA
D

The passage implies that at the beginning of the life of IRC + 10216, its mass was approximately

(A) 7.0 $$M \odot$$
(B) 6.0 $$M \odot$$
(C) 5.0 $$M \odot$$
(D) 1.4 $$M \odot$$
(E) 1.0 $$M \odot$$

Spoiler: :: OA
B

The view to which line 18 refers serves to

(B) undermine a previously held theory
(C) take into account data previously held to be insignificant
(D) resolve a controversy
(E) question new methods of gathering data

Spoiler: :: OA
A

It can be inferred from the passage that the author assumes which of the following in the discussion of the rate at which IRC + 10216 loses mass?

(A) The circumstellar cloud surrounding IRC + 10216 consists only of CO and $$NH_3$$ molecules.
(B) The circumstellar cloud surrounding IRC + 10216 consists of material expelled from that star.
(C) The age of a star is equal to that of its circumstellar cloud.
(D) The rate at which IRC + 10216 loses mass varies significantly from year to year.
(E) Stars with a mass greater than 6 $$M \odot$$ lose mass at a rate faster than stars with a mass less than 6 $$M \odot$$ do.

Spoiler: :: OA
B

According to information provided by the passage, which of the following stars would astronomers most likely describe as a planetary nebula?

(A) A star that began its life with a mass of 5.5 $$M \odot$$, has exhausted its nuclear fuel, and has a core that is visible to astronomers
(B) A star that began its life with a mass of 6 $$M \odot$$, lost mass at a rate of 1 $$M \odot$$ per 10,000 years, and exhausted its nuclear fuel in 40,000 years
(C) A star that has exhausted its nuclear fuel, has a mass of 1.2 $$M \odot$$, and is surrounded by a circumstellar cloud that obscures its core from view
(D) A star that began its life with a mass greater than 6 $$M \odot$$, has just recently exhausted its nuclear fuel, and is in the process of releasing massive amounts of gravitational energy
(E) A star that began its life with a mass of 5.5 $$M \odot$$, has yet to exhaust its nuclear fuel, and exhibits a rate of mass loss similar to that of IRC + 10216

Spoiler: :: OA
A

Which of the following statements would be most likely to follow the last sentence of the passage?

(A) Supernovas are not necessarily the most spectacular events that astronomers have occasion to observe.
(B) Apparently, stars that have a mass of greater than 6 $$M \odot$$ are somewhat rare.
(C) Recent studies of CO and $$NH_3$$ in the circum-stellar clouds of stars similar to IRC + 10216 have led astronomers to believe that the formation of planetary nebulas precedes the development of supernovas.
(D) It appears, then, that IRC + 10216 actually represents an intermediate step in the evolution of a giant star into a planetary nebula.
(E) Astronomers have yet to develop a consistently accurate method for measuring the rate at which a star exhausts its nuclear fuel.

Spoiler: :: OA
D

Which of the following titles best summarizes the content of the passage?

(A) New Methods of Calculating the Age of Circumstellar Clouds
(B) New Evidence Concerning the Composition of Planetary Nebulas
(C) Protoplanetary Nebula: A Rarely Observed Phenomenon
(D) Planetary Nebulas: An Enigma to Astronomers
(E) The Diminution of a Star's Mass: A Crucial Factor in Stellar Evolution

Spoiler: :: OA
E

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Originally posted by carcass on 10 Feb 2019, 03:28.
Last edited by SajjadAhmad on 14 Oct 2019, 03:55, edited 1 time in total.
Updated - Complete topic (970).
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Re: Until recently astronomers have been puzzled by the fate of red giant  [#permalink]

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15 Feb 2019, 03:24
Top Contributor
Nobody did attempt this amazing yet super tough yet official passage ??

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Re: Until recently astronomers have been puzzled by the fate of red giant  [#permalink]

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15 Feb 2019, 22:27
Hello,

Can someone explain the reasoning behind the questions 5&6?
For 5th my logic is: As the analysis has bee done only for two things CO and NH3 so it was assumed by the scientists that there are no other elements present in the star.
For 6th I was dumbstruck, so no explanation.Also, please explain how do we go about such questions?

Thanks!
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Re: Until recently astronomers have been puzzled by the fate of red giant  [#permalink]

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15 Feb 2019, 23:21
1
9 mins, All correct, had a doubt in Q5, lets begin now

D B A B A D E

Once you understand what the passage was all about, it will be easy to comprehend the questions, said that, i took 3 mins, to just do that

Q1 The primary purpose of the passage is to
(A) offer a method of calculating the age of circumstellar clouds
(B) describe the conditions that result in a star's expiring as a supernova
(C) discuss new evidence concerning the composition of planetary nebulas
This was not the overall idea of the passage
(D) explain why fewer stars than predicted expire supernovas
It starts in the beginning paragraph, in which a general discussion was started, in second paragraph, evidence was stated as to why?? and in the last passage, they concluded by saying that they(astronomers) were creating a hype which was quite commonly known to optical astronomers

(E) survey conflicting theories concerning the composition of circumstellar clouds

Q2 The passage implies that at the beginning of the life of IRC + 10216, its mass was approximately

(A) 7.0 $$M \odot$$
(B) 6.0 $$M \odot$$
From these lines it was quite prominent
suggest that stars that begin their lives with masses around 6 $$M \odot$$ shed sufficient material to drop below the critical value of 1.4 $$M \odot$$. IRC + 10216,

(C) 5.0 $$M \odot$$
(D) 1.4 $$M \odot$$
(E) 1.0 $$M \odot$$

Q3 The view to which line 18 refers serves to

Come in terms with

(B) undermine a previously held theory
(C) take into account data previously held to be insignificant
(D) resolve a controversy
(E) question new methods of gathering data

Q4 It can be inferred from the passage that the author assumes which of the following in the discussion of the rate at which IRC + 10216 loses mass?

(A) The circumstellar cloud surrounding IRC + 10216 consists only of CO and $$NH_3$$ molecules.
(B) The circumstellar cloud surrounding IRC + 10216 consists of material expelled from that star.
From these lines
This implies that some stars can shed huge amounts of the matter very quickly and thus may never expire as supernovas.

(C) The age of a star is equal to that of its circumstellar cloud.
(D) The rate at which IRC + 10216 loses mass varies significantly from year to year.
(E) Stars with a mass greater than 6 $$M \odot$$ lose mass at a rate faster than stars with a mass less than 6 $$M \odot$$ do.

Q5 According to information provided by the passage, which of the following stars would astronomers most likely describe as a planetary nebula?

For me there were only 2 contenders here,A & D, because they were directly speaking about these lines
{Astronomers suggest that stars like IRC + 10216 are actually "protoplanetary nebulas"—old giant stars whose dense cores have almost but not quite rid themselves of the fluffy envelopes of gas around them. Once the star has lost the entire envelope, its exposed core becomes the central star of the planetary nebula and heats and ionizes the last vestiges of the envelope as it flows away into space. This configuration is a full-fledged planetary nebula, long familiar to optical astronomers.}

(A) A star that began its life with a mass of 5.5 $$M \odot$$, has exhausted its nuclear fuel, and has a core that is visible to astronomers

(D) A star that began its life with a mass greater than 6 $$M \odot$$, has just recently exhausted its nuclear fuel, and is in the process of releasing massive amounts of gravitational energy
IMO,Now when i think about this again and match with the bold part, it is releasing heat, but not gravitational energy, So Out

Q6 Which of the following statements would be most likely to follow the last sentence of the passage?

(A) Supernovas are not necessarily the most spectacular events that astronomers have occasion to observe.
(B) Apparently, stars that have a mass of greater than 6 $$M \odot$$ are somewhat rare.
rarity cannot be implied, in the last line itself the passage mentions that its quite common

(C) Recent studies of CO and $$NH_3$$ in the circum-stellar clouds of stars similar to IRC + 10216 have led astronomers to believe that the formation of planetary nebulas precedes the development of supernovas.
Cannot be implied as per the intent of the passage

(D) It appears, then, that IRC + 10216 actually represents an intermediate step in the evolution of a giant star into a planetary nebula.
Yes this supports the intent of the whole passage to say that
"protoplanetary nebulas"—old giant stars whose dense cores have almost but not quite rid themselves of the fluffy envelopes of gas around them
and once they lose that they will turn into a planetary nebula

If we have understood the intent of the passage , this was the only next plan of action.

(E) Astronomers have yet to develop a consistently accurate method for measuring the rate at which a star exhausts its nuclear fuel.

Q 7 Which of the following titles best summarizes the content of the passage?

(A) New Methods of Calculating the Age of Circumstellar Clouds
No methods were discussed per se

(B) New Evidence Concerning the Composition of Planetary Nebulas

(C) Protoplanetary Nebula: A Rarely Observed Phenomenon
Again its not a rare event

(D) Planetary Nebulas: An Enigma to Astronomers
its not an enigma, some people do know about it.

(E) The Diminution of a Star's Mass: A Crucial Factor in Stellar Evolution
reduction in size was discussed, this can act as an apt title
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Re: Until recently astronomers have been puzzled by the fate of red giant  [#permalink]

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16 Feb 2019, 10:22
apovit wrote:
Hello,

Can someone explain the reasoning behind the questions 5&6?
For 5th my logic is: As the analysis has bee done only for two things CO and NH3 so it was assumed by the scientists that there are no other elements present in the star.
For 6th I was dumbstruck, so no explanation.Also, please explain how do we go about such questions?

Thanks!
u1983

apovit
Q5. According to information provided by the passage, which of the following stars would astronomers most likely describe as a planetary nebula?

(A) A star that began its life with a mass of 5.5 M⊙M⊙, has exhausted its nuclear fuel, and has a core that is visible to astronomers
=> planetary nebula：- expire much more peacefully, most massive stars manage to lose sufficient material that their masses drop below the critical value of 1.4 M⊙M⊙ before they exhaust their nuclear fuel.
- begin their lives with masses around 6 M⊙ shed sufficient material to drop below the critical value of 1.4M⊙
- This configuration is a full-fledged planetary nebula, long familiar to optical astronomers.
Combined these 3 points i chose A

(B) A star that began its life with a mass of 6 M⊙M⊙, lost mass at a rate of 1 M⊙M⊙ per 10,000 years, and exhausted its nuclear fuel in 40,000 years
(C) A star that has exhausted its nuclear fuel, has a mass of 1.2 M⊙M⊙, and is surrounded by a circumstellar cloud that obscures its core from view
(D) A star that began its life with a mass greater than 6 M⊙M⊙, has just recently exhausted its nuclear fuel, and is in the process of releasing massive amounts of gravitational energy
(E) A star that began its life with a mass of 5.5 M⊙M⊙, has yet to exhaust its nuclear fuel, and exhibits a rate of mass loss similar to that of IRC + 10216

Q6. Which of the following statements would be most likely to follow the last sentence of the passage?

(A) Supernovas are not necessarily the most spectacular events that astronomers have occasion to observe.
(B) Apparently, stars that have a mass of greater than 6 M⊙M⊙ are somewhat rare.
(C) Recent studies of CO and NH3NH3 in the circum-stellar clouds of stars similar to IRC + 10216 have led astronomers to believe that the formation of planetary nebulas precedes the development of supernovas.
(D) It appears, then, that IRC + 10216 actually represents an intermediate step in the evolution of a giant star into a planetary nebula. => "But what place does IRC + 10216 have in stellar evolution? ", the last passage is opened with this question so it should be ended up with an answer related.
(E) Astronomers have yet to develop a consistently accurate method for measuring the rate at which a star exhausts its nuclear fuel.
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Re: Until recently astronomers have been puzzled by the fate of red giant   [#permalink] 16 Feb 2019, 10:22
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