Clear Sky.
1 ---> Light from stars visible.
2 ---> Light from satellites visible.
3 ---> Light from airplanes (passing by) visible.
Apart from the change in color, the light from 1 and 2 seems like its trembling but not 3.
Why is that so?
The light from stars comes through the atmosphere and gets distorted like light passing through a pool. Stars are particularly prone to this effect because they are single points and the light only follows one path to your eye.
Planets don't twinkle as much because they are tiny circles and the light from either edge of the planet travels slightly different paths to your eye.
So for a planet to twinkle multiple paths would have to be blocked at once which is less likely.
Satellites are also less prone to twinkling because they are not points. Planes on the other hand will never twinkle because they are large objects whose light doesn't even need to pass through the entire atmosphere.
