Question

What is the reason for twinkling of stars?

Hint:

Twinkling is most noticeable on clear nights, especially when stars are low in the sky. It’s less noticeable in planets, which tend to shine with a steadier light.

Answer 1

The twinkling of stars, also known as stellar scintillation, is caused by the atmospheric refraction of starlight. The Earth's atmosphere consists of several layers of air, each with a different temperature and density. When starlight passes through these layers, it bends (refracts) due to the changing refractive indices. As the light moves through the atmosphere, it is refracted in irregular ways because of the constantly changing air conditions. This causes the brightness and position of the star to appear to fluctuate, leading to the twinkling effect.
The effect is more pronounced for stars because they are so far away that they appear as point sources of light. As a result, the bending of light is more noticeable.
Planets, on the other hand, appear as small disks, so the light they emit is less affected by atmospheric refraction, and they do not twinkle as much as stars.