Exam-style question
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What does a blue shift in a star's spectrum indicate in the context of radial velocity?.
- A.The star is moving away from the observer
- B.The star is moving towards the observer
- C.The star's temperature is increasing
- D.The star has a higher luminosity
Model answer
What a good answer should say
- The star is moving towards the observer
Explanation
Why this works
The evidence shows that a blue shift occurs when the wavelengths of light from a star are compressed, indicating that the star is moving closer to the observer. This implies that the gravitational influence of an orbiting planet is causing the star's motion.
Therefore, the conclusion is that a blue shift indicates the star is moving towards the observer.
Common mistake
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