Exam-style question
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If two stars have the same luminosity but different spectral classes, what can be inferred about their temperatures?.
- A.The star with the earlier spectral class is hotter.
- B.The star with the later spectral class is hotter.
- C.Both stars have the same temperature.
- D.Temperature cannot be inferred from spectral class.
Model answer
What a good answer should say
- The star with the earlier spectral class is hotter.
Explanation
Why this works
Define both: Earlier spectral classes (O, B, A) are hotter than later classes (F, G, K, M). Identify key difference: Earlier classes have higher surface temperatures.
Explain when each applies: When comparing stars of equal luminosity, the one with the earlier class must be hotter to produce the same energy output. Conclude: The earlier class star is hotter.
Common mistake
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