Stars twinkle but planets do not twinkle because ?

(1) they emit light of a constant intensity.
(2) their distance from the earth does not change with time.
(3) they are very far away from the earth resulting in decrease in intensity of light.
(4) they are nearer to the earth and hence we receive a greater amount of light and therefore minor variations in intensity are not noticeable.

Correct Answer : (4) Stars twinkle but planets do not twinkle because they are nearer to the earth and hence we receive a greater amount of light and therefore minor variations in intensity are not noticeable.

Explanation:

Stars are the primary sources of light and they are situated very far from earth.

Light of the star is bent many times and in random directions as light is bent when it hits a change in density. Also, Passing through the atmosphere, the light constantly shifts by bouncing off particles in the air and change in density of atmosphere. This random refraction results in the star winking out – twinkling.

However, the much closer planets appear instead as tiny disks in the sky. 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 stars twinkle but planets do not twinkle.

See Also

Reference

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