Continuously changing atmosphere reflect light from the stars by different amounts from one moment to the other. When atmosphere refracts more starlight towards us, the stars appear to be bright and when the atmosphere refracts less starlight, then the stars appear to be dim.
However the planets are nearer to us than the stars, they appear to be comparatively bigger to us so they cannot be considered as a point source, hence Ans. fine particles in air. no twinkling is seen.
