why do stars twinkle but planets do not?explain?
The twinkling of a star is due to atmospheric refraction of
starlight. The starlight, on entering the earthâs atmosphere,
undergoes refraction continuously before it reaches the earth.
The atmospheric refraction occurs in a medium of gradually
changing refractive index. Since the atmosphere bends
starlight towards the normal, the apparent position of the
star is slightly different from its actual position.
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 â the star sometimes appears brighter,
and at some other time, fainter, which is the twinkling effect.
The planets are much closer to the
earth, and are thus seen as extended sources. If we consider a planet as
a collection of a large number of point-sized sources of light, the total
variation in the amount of light entering our eye from all the individual
point-sized sources will average out to zero, thereby
nullifying the twinkling effect.
Hope this clarifies your doubt.