Question

why stars twinkle while planets don't?

Answer 1

Dear Student ,
Stars emit their own light and they twinkle due to the atmospheric refraction of light. Stars are very far away from the earth. Hence, they are considered as point sources of light. When the light coming from stars enters the earth’s atmosphere, it gets refracted at different levels because of the variation in the air density at different levels of the atmosphere. When the star light refracted by the atmosphere comes more towards us, it appears brighter than when it comes less towards us. Therefore, it appears as if the stars are twinkling at night.
Planets are very close to us as compared to the distance between stars and earth. They appear as small discs of light (the reflected light from the sun). Each tiny point in this disc can be considered as point sources of light. These different points produce either brighter or dimmer effect in such a way that the average of brighter and dimmer effect is zero. Hence, the twinkling effects of the planets are nullified and they do not twinkle.
In a very turbulent weather a planet may appear to twinkle because of the disturbance in the air through which the light is travelling.

Regards