The phenomenon behind twinkling of stars is known as ‘atmospheric refraction’.

When the light from the stars enters the atmosphere of earth, the light from stars undergoes the refraction due to the different density of atmospheric gases (air) on different levels before coming to us. So the refractive index change continuously and refract the light coming from the stars in different amount. In this way, the starlight reaching our eyes increase and decrease due to the uneven density of atmospheric air present in its paths. That’s why they appear to twinkle.

Planets do not twinkle because they are larger in size and very close to us in compared to stars which are far away from us and large in size. So as we know there are many other planets in our solar system. So planets can be taken as a collection of large number of point sized sources of light. As they are in group, so the starlight that comes from them to our eyes as an individual which basically gives that twinkling effect will be average out of zero, which nullify the twinkling effect of each other.

• This reply was modified 2 years, 11 months ago by  Kidpid.