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Difficulty: EasyPrimary Purpose of the Whole Text

Prior to the discovery of 51 Pegasi b in 1995, astronomers assumed that all planetary systems would resemble our own, with rocky planets close to the host star and gas giants orbiting far away. However, 51 Pegasi b, a gas giant, was found orbiting extremely close to its star. This unexpected discovery forced scientists to revise their models of planetary formation, introducing the concept of planetary migration to explain how a massive planet could end up so close to its star. Consequently, this breakthrough reshaped our understanding of the cosmos and the diversity of planetary systems.

Which choice best states the main purpose of the text?

  1. A
    To outline the differences in orbit and composition between rocky planets and gas giants.
  2. B
    To criticize early astronomers for refusing to accept new models of planetary migration.
  3. To explain how the discovery of a particular planet led scientists to revise their theories about how planetary systems form.Answer
  4. D
    To argue that 51 Pegasi b is the largest and most massive gas giant in the cosmos.

Answer

The correct answer is the option explaining that the text's purpose is to show how a specific planetary discovery challenged and updated scientists' models of planetary formation.
The passage describes the discovery of 51 Pegasi b and explains that because its close orbit challenged existing theories, astronomers had to revise their models of planetary formation. The correct option accurately summarizes this main objective of the text.

Step-by-Step Solution

1
Identify the primary topic and narrative development of the passage.
The passage details how the discovery of 51 Pegasi b contradicted existing planetary system models, which then led scientists to revise their theories by introducing planetary migration.
Understanding the core narrative arc is necessary to determine the primary purpose of the whole text.
2
Analyze each option to see which one summarizes this overall development rather than a narrow detail or an unsupported argument.
Only one option captures the relationship between the discovery of the planet and the subsequent revision of planetary formation theories.
The correct answer must represent the primary purpose of the text as a whole.

Key Concept

Primary Purpose of the Whole Text
Estimated Time:1m 0s
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Primary Purpose of the Whole Text

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