The Human Eye and the Colourful World · Class 10 · CBSE Science
Why do stars twinkle at night, while planets do not?
Practice question from The Human Eye and the Colourful World (Class 10 · CBSE Science), with the correct answer and a step-by-step solution.
hard · Subjective · Q-3E85D2
Why do stars twinkle at night, while planets do not?
Answer: Stars twinkle because they are distant point-like sources of light, and the continuously changing refractive index of the earth's atmosphere causes the starlight to fluctuate in apparent position and brightness. Planets, being much closer, act as extended sources of light consisting of a collection of numerous point-sources, the total variation of light entering the eye from all points averages out to zero, neutralizing the twinkling effect.
Solution
Atmospheric refraction causes starlight to bend irregularly. Point-sized stars fluctuate significantly in brightness and position (twinkling), whereas extended planets do not show noticeable twinkling.
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