The Milky Way galaxy is composed of millions of stars in a relatively flat structure containing a thin disk and...
GMAT Information and Ideas : (Ideas) Questions
The Milky Way galaxy is composed of millions of stars in a relatively flat structure containing a thin disk and a thick disk. Based on computer simulations and analysis of data on the brightness, position, and chemical composition of about 250,000 stars in the thick disk (collected from two telescopes, one in China and one orbiting in space), astrophysicists Maosheng Xiang and Hans-Walter Rix claim that the thick disk of the Milky Way formed in two distinct phases rather than a single one.
Which finding, if true, would most directly support the researchers' claim?
The telescopes used by the researchers have detected stars of similar ages in galaxies other than the Milky Way.
There's an age difference of about 2 billion years between certain stars in the thick disk.
The thin disk contains about twice as many stars that can be seen from Earth as the thick disk does.
The stars in the Milky Way tend to have very similar chemical compositions.
Step 1: Decode and Map the Passage
Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| 'The Milky Way galaxy is composed of millions of stars in a relatively flat structure containing a thin disk and a thick disk.' |
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| 'Based on computer simulations and analysis of data on the brightness, position, and chemical composition of about 250,000 stars in the thick disk (collected from two telescopes, one in China and one orbiting in space),' |
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| 'astrophysicists Maosheng Xiang and Hans-Walter Rix claim that the thick disk of the Milky Way formed in two distinct phases rather than a single one.' |
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Provide Passage Architecture & Core Elements
Main Point: Researchers claim the Milky Way's thick disk formed through two distinct phases rather than a single formation period.
Argument Flow: The passage establishes the structure of the Milky Way, then describes comprehensive research methods used to study the thick disk, leading to the researchers' claim that this disk formed in two separate phases rather than one continuous process.
Step 2: Interpret the Question Precisely
What's being asked? Which finding would most directly support the researchers' two-phase formation claim
What type of answer do we need? Evidence that would strengthen or validate their conclusion
Any limiting keywords? 'most directly support' - we need the strongest, most relevant evidence for their specific claim
Step 3: Prethink the Answer
- If the thick disk really formed in two distinct phases rather than one, we'd expect to see clear evidence in the star data that points to two separate formation periods
- This could be: Stars of notably different ages that cluster into two groups, Different chemical compositions suggesting different formation environments, or Spatial patterns showing two distinct formation events
- The key is that 'two phases' means two separate time periods or processes, so we need evidence that shows this separation clearly rather than continuous formation
The telescopes used by the researchers have detected stars of similar ages in galaxies other than the Milky Way.
✗ Incorrect
- This talks about similar ages in other galaxies, not age differences in our thick disk
- Doesn't address whether our thick disk formed in one phase or two
There's an age difference of about 2 billion years between certain stars in the thick disk.
✓ Correct
- A 2 billion year age difference between stars in the thick disk directly indicates two separate formation periods
- This matches our prethinking perfectly - if there are two phases, stars should show distinct age groups
The thin disk contains about twice as many stars that can be seen from Earth as the thick disk does.
✗ Incorrect
- Compares star counts between thin and thick disks
- Doesn't provide any information about formation phases or timing
The stars in the Milky Way tend to have very similar chemical compositions.
✗ Incorrect
- Similar chemical compositions would actually suggest continuous formation conditions
- This would support single-phase formation rather than two distinct phases