PT128.S4.P3.Q14 > Analytics

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In the early 1900s, most astronomers mistakenly believed that 66 percent of the sun's substance was iron. ███

Old perspective · Sun was mostly made of iron

Payne's perspective · Sun is mostly hydrogen and helium

Payne's view initially was resisted by astronmers. But eventually it was accepted by them.

Evidence supporting old perspective · Known asteroids contain iron, and spectroscopy

Spectroscopy involves identifying chemical from light patterns. This seemed to show that sun was mostly iron.

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Puzzling aspect of old perspective · How could something made mostly of iron generate the high energy output of the sun?

Kelvin's answer · Sun was contracting, which raised sun's temperature and generated energy

Payne's response · Fossil record showed Kelvin's answer was wrong; need to re-examine the iron theory

If sun contracted as Kelvin said, the sun would be much younger than fossil record showed it was. So, iron theory might be wrong and we need to look at the spectroscopic evidence again.

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Payne's interpretation of evidence · Spectroscopic data consistent with sun being 90% hydrogen and the rest mostly helium

Although sun has some iron, preconceptions about sun being iron led to prior interpretation that sun was mostly iron.

Astronomers' response · Payne was looking only at outer layer of sun

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Confirmation of Payne's perspective · Later discovery of nuclear fusion helped confirm Payne was right

During Payne's time, we didn't know how something mostly helium/hydrogen could produce as much energy the sun. Now, we know that the sun's energy is produced by nuclear fusion.

Passage Style

Critique or debate

Phenomenon-hypothesis (RC)

14.

The passage provides enough information ██ ██████ █████ ███ ██ ███ █████████ ██████████

Does the iron ███████ ██ █████ ██████ ██ ███████ ██ ███ █████ █████

Although the passage does indicate that Earth has iron, it doesn’t indicate what proportion of Earth’s mass is iron.

Who first proved ████ ███ ███ █████████ ████ ████ ████████ ██ ███████ ███████

The passage doesn’t identify the first person to prove that the sun generates heat through nuclear fusion.

13%

Do any objects ██ ███ █████ ██████ █████ ████ █████ ███ ███ ███ ███████ █████

Answered.

68%

What percentage of ███ █████ ████ ██ ████████ ██ █████

Not answered, because although Payne proposed that 90 percent of the sun is hydrogen and helium, this doesn’t imply that 10 percent is iron. Rather, 10% is iron and “other elements found on Earth.”

Can the fusion ██ █████ █████ ████ ████████ █████ ███████ ███████

The passage doesn’t indicate whether the fusion of other kinds of atoms can produce energy.

PrepTest 128 - Section 4 - Passage 3 - Question 14

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