Question

explain twinkling of a star. Why does a planet not twinkle.

Answer 1

Twinkling of stars is due to atmospheric refraction and stars are far way while planet's are not at that distance so planet's don't appears to be 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.