Question

Stars twinkle but planets do not twinkle because

• A. Stars emit their own light but planets receive light from the stars
• B. Stars do not from a part of solar system
• C. Stars from a point source of light while planets are considered as a collection of a large number of point sources of light
• D. During refraction of star light from the atmosphere, star light bends more towards the normal as compared to the planets

Answer 1

Answer: (C)

Stars from a point source of light while planets are considered as a collection of a large number of point sources of light

Light of the star is bent many times and in random directions as light is bent when it hits a change in density. This random refraction results in the star winking out - twinkling.

Planets are closer to Earth and so appear as tiny disks in our sky.

The light from these little disks is also refracted by Earth’s atmosphere, as it travels toward our eyes. Due to the planets’ apparent closeness to Earth, the light coming from these celestial bodies does not bend much due to Earth’s atmosphere. Also being not a point source but appearing as disks, they comprise of several point sources- lights of which are coming at the same time. So a deviation in light path of one point source can cancel with deviations of other and would average out to give rise to a steady shine. Therefore, the light coming from our solar system’s planets does not appear to twinkle like stars.