Explain why the planets do not twinkle but the stars twinkle.
Planets are closer to earth and are seen as-extended source of light i.e…the collection of large no. of point sized sources of light. Therefore the total amount of light entering our eyes from all individual point source will nullify the twinkling effect.
Twinkling of Star: It is due to the atmospheric refraction.
Distant star act like a point source of light. As the beam of starlight keeps deviating from its path, the apparent position of star keeps on changing because physical condition of Earth’s atmosphere is not stationary.
Hence the amount of light enters our eyes fluctuate light, which are some times bright and some times fainted. This is the “Twinkling effect of star”.