What causes the twinkling of stars?

Question

What causes the twinkling of stars?

1. A. Atmospheric refraction of starlight (Correct answer)
2. B. Dispersion of starlight
3. C. Scattering of starlight
4. D. Prism effect

Correct Answer

Option A — Atmospheric refraction of starlight

Detailed Solution & Explanation

The correct answer is Atmospheric refraction of starlight.

Key Points

• Stars twinkle due to atmospheric refraction — their light bends as it passes through layers of the atmosphere with varying density and temperature, causing the apparent position and brightness to fluctuate.

Additional Information

• Stars twinkle — stellar scintillation — because their light is refracted by turbulent atmospheric layers of varying density and temperature.
• Planets do not twinkle appreciably: they are near enough to present a small disc rather than a point, so the fluctuations average out.
• The same refraction makes the Sun visible for a few minutes before actual sunrise and after actual sunset, and makes stars appear slightly higher than they are.
• Other everyday refraction effects: the apparent bending of a stick in water, the shallower look of a pond, and mirages.