MCQ Detailed View

Stars appear to twinkle in the night sky because of a phenomenon called atmospheric refraction. When starlight enters the Earth’s atmosphere, it passes through many layers of air. Each layer of air has a slightly different temperature and density, which causes the light to bend or refract multiple times.

This constant bending makes the path of starlight slightly unstable. As the atmosphere keeps changing due to moving air currents, temperature differences, and varying pressure, the light from a star seems to shift and change in brightness. This is why to the human eye, the star appears to twinkle.

The effect is stronger for stars near the horizon, because their light has to travel through a thicker layer of the atmosphere compared to stars overhead. That is why stars near the horizon often appear to flicker more.

It is important to note that stars do not actually change their brightness rapidly. The twinkling is only an effect caused by Earth’s atmosphere. In space, or when observed through telescopes from above the atmosphere, stars do not twinkle. This is why astronomers place telescopes in high mountains or even in space (like the Hubble Space Telescope) to avoid atmospheric interference.

Planets, on the other hand, do not twinkle as much as stars. This is because planets are much closer to Earth and appear as tiny disks of light rather than sharp points. The larger apparent size of planets averages out the atmospheric disturbance, so they look steadier compared to stars.

Therefore, the correct answer is that stars twinkle due to a series of refractions in the Earth’s atmosphere.