Difference between Twinkling of stars and planets
Twinkling of stars
1) Stars are situated from long distance from the surface of earth.
2) When we observe the stars from surface of earth, the intensity of light emitted by stars appears to be changing continuously.
3) Light emitted by stars enters the atmosphere and suffers multiple refractions due continuous changes in refractive indices of medium and then reaches to observer.
4) When the refraction is takes place more toward normal, position of star appears slightly higher than its original position. See the following diagram.
5) This position of the star is not stationary and keeps on changing slightly, since the physical conditions of the earth’s atmosphere like temperature and air are not stationary.
6) The continuous change in position of star sends fluctuating intensity towards the observer which makes star sometimes brighter or dim.
7) This is known as twinkling of stars.
Planets
1) Planets are situated at smaller distances from the earth as compared to stars.
2) When we observe the planets from the surface of earth, the intensity emitted by the planet are appears to be constant. Hence planets do not twinkle.
3) Planets can be considered as composed of large number of stars in it.
4) Due to this the average intensity numbers of stars appears bright is always equals to average number of stars appears dim.
5) This cancels the effect of twinkling and planets acts as steady light source.
6) Thus planets do not twinkle as like stars.