Why do stars twinkle? This is a very common question which arises in front of everyone.It may be asked by your children, student, or maybe it suddenly pops into your brain.
The twinkling of a star is due to atmospheric refraction of starlight. The starlight, on entering the earth’s atmosphere, undergoes refraction continuously before it reaches the earth.
In our atmosphere, there are various layers of air which are having different densities, due to which their refractive indices are also different. When a ray of light enters the atmosphere, it undergoes multiple refractions.
The atmospheric refraction occurs in a medium of gradually changing refractive index. Since the stars are very distant, they approximate point-sized sources of light.
As the path of rays of light coming from the star goes on varying slightly, the apparent position of the star fluctuates and the amount of starlight entering the eye flickers – the star sometimes appears brighter, and at some other time, fainter, which is the twinkling effect.