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Sub 505 Level|   Science|   Short Passage|      
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armaankumar
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During the past 40 years, the star FG Sagittae has changed color from 02 Sep 2022, 01:17
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armaankumar
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P1: Presenting evidence for FG’s temp. drop (Color change, change in size-> Pulses and Luminosity)
P2: Provides an observation connected to total luminosity evidence in P1
All this passage is about is presenting evidence for a star’s change in temperature and size

1. According to the passage, if the luminosity of a given star has remained constant while its temperature has decreased, what will also necessarily be true of the star?
Type: Detail
Focus of the question: Luminosity and temperature decrease

(A) The star will have increased in size.
The last sentence of the first paragraph says “if one of the two factors has decreased while over the same period luminosity has remained constant, the other factor must have increased.”
The other factor is size=>Radius has increased


(B) The star's apparent brightness will have substantially increased.
Even though the second paragraph says “the total amount of light FG Sagittae emits has not changed, the star now appears brighter in the sky than it did 40 years ago.”
It is not necessarily true for the case of every star.

(C) The star will have changed from blue to yellow in color.
Even though FG Sagittae changed color from blue to yellow, it is not neccesarily true that every star will change from blue to yellow

(D) The star's pulsation period will have shortened somewhat.
It is true that a star's pulsation period is determined by its radius. However, we know that the star’s pulsation period increasing when it’s size increases, and the radius of the star increases if the luminosity of a given star has remained constant while its temperature has decreased.

(E) The star will have begun to emit less visible light than it once did.
Even though the second paragraph says “the total amount of light FG Sagittae emits has not changed, the star now appears brighter in the sky than it did 40 years ago.”
This answer choice may or may not be true for any star.

2. It can be inferred from the passage that the phrase “two independent pieces of observational evidence” (see highlighted text) refers to observations made of which of the following?
Type: Detail
Focus of the question: Observational Evidence

We can see that the first paragraph says “Its cooling is probably due to a *rapid increase in its size*, an inference that is indirectly supported by two independent pieces of observational evidence”

The two observational evidences are the star’s pulsation period and its total luminosity.

(A) FG Sagittae's apparent brightness in the sky and its temperature
Trap: Distortion
The brightness of the star makes up a part of total luminosity but is not what the observational evidence is directly referring to.

(B) FG Sagittae's color and its temperature
The observational evidence is supporting an inference about the size of the star not the color.

(C) The amount of light FG Sagittae emits across all wavelengths and its pulsation period
This answer choice covers both the observational evidences.

(D) FG Sagittae's radius and its color
Trap: Distortion
The observational evidences refer to the pulsation period and the total luminosity from which scientists infer about the star’s radius and its color.

(E) The amount of light FG Sagittae emits across all wavelengths and the amount it emits at ultraviolet wavelengths
Trap: Half Right answer choice
This answer choice starts of correct but the observation evidence is not referring to the amount of uv wavelengths emitted.
Show more

3. The author of the passage is primarily concerned with
Type: Primary Purpose
We have to be really careful about the verbs used in the answer choices: Whether they are argumentative or descriptive

(A) analyzing the effects of a particular phenomenon
Trap: Too Narrow
The author is only describing the effects of the phenomenon to which the observational evidences refer to

(B) presenting evidence in favor of a given explanation
All this passage is about is presenting evidence for a star’s change in temperature and size

(C) reporting new data that undermines an accepted view
There is no data mentioned that is undermining an accepted view.

(D) evaluating the arguments in favor of a given hypothesis
Trap: Wrong Verb
The author is presenting evidences for a given explanation. There are no disagreements or arguments mentioned in the passage.

(E) presenting an interesting sidelight on a complex phenomenon
Trap: Too narrow
Only the second paragraph talks about an interesting sidelight. This answer choice misses what’s said in the first paragraph.
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wickedvikram
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During the past 40 years, the star FG Sagittae has changed color from 24 Apr 2023, 03:18
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I think Question 2 was deliberately formed to confuse us. The language confused me into thinking the reasons for those observations, whereas it was simply asking the two observations.
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During the past 40 years, the star FG Sagittae has changed color from 31 Aug 2024, 10:33
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Hello from the GMAT Club VerbalBot!

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