Question

why stars twinkle where as planet do not twinkle

Answer 1

Stars have their own light but planets do not. Well this is irrelevant to say that stars twinkle. Stars dont twinkle . They appear to twinkle only when viewed from surface of the earth. when starlight enters the atmosphere of earth it goes through different temperatures and densities. This results in bouncing back of starlight in different directions which gives the appearance of twinkling.

Answer 2

Explanation:

Planets are much closer to the earth and are seen as extended sources. So, a planet may be considered as a collection of a large number of point-sized light sources. Although light coming from individual point-sized sources flickers but the total amount of light entering our eye from all the individual point-sized sources average out to be constant. Thereby, planets appear equally bright and there is no twinkling of planets.