Stars twinkle when observed from Earth, but the Sun does not appear to twinkle even though it is also a star.…

Question

Stars twinkle when observed from Earth, but the Sun does not appear to twinkle even though it is also a star. Explain why the Sun does not produce a twinkling effect, referring to the relevant physical property that distinguishes it from distant stars as seen from Earth.

Accepted Answer

## Model Answer Stars twinkle because they are very far away and appear as **point-sized sources** of light. As starlight passes through the ever-changing layers of the atmosphere, continuous refraction causes the amount of light reaching the eye to flicker, producing the twinkling effect. The Sun, though also a star, is much closer to Earth and therefore appears as an **extended source** (not a point source). When light from a large number of point-sized regions of the Sun's disc is considered, the fluctuations in light from all these points average out to zero, nullifying any twinkling effect. *Source: Chapter 10, Section 10.5 – Atmospheric Refraction* --- ## Explanation - The key distinction examiners look for is **point source vs. extended source**. - Mention that stars are distant → point-sized; Sun is close → extended source. - State clearly that for an extended source, individual fluctuations cancel out → no twinkling. - Do not just say "Sun is closer" — you must link it to the…

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