TWINKLE,TWINKLE, LITTLE STAR

Twinkle, twinkle, little star,
How I wonder …

WHY DO STARS TWINKLE?

Twinkle,twinkle , little star by GIPHY

To explain this phenomenon, first, we need to know the exact definition of twinkling. The scientific name of the twinkling stars is astronomical scintillation. Twinkling/ scintillation, is a general term for variations in apparent brightness or position of a distant luminous object when viewed through a certain medium.

The main reason for this occurrence is due to the presence of thick layers of air turbulence (moving air) in the Earth’s atmosphere. This air turbulence causes twinkling because it is a continuous process of changing how starlight bent. In other words, as a starlight travels into our atmosphere, each stream of starlight is refracted .This refraction change the direction of the star, slightly due to the temperature gradient and different density layers in the Earth’s atmosphere.The random refraction of the starlight results in the twinkling of the star.

Hence, stars tend to twinkle more when they are closer to the horizon and windy (extreme turbulent) nights. WHY?  This is because the light of stars near the horizon has to travel through denser layer of air compared to the light of stars overhead. Thus, more refraction occur. Above the atmosphere, if we viewed from outer space (or from a planet that didn’t have an atmosphere), stars do not twinkle at all.

Why do Stars Twinkle?

A misconception holds that planets don’t twinkle in our sky. In reality, they actually do, but planets shine more steadily. This is because they are closer to the Earth,hence they appear big enough that the twinkling is not realizable although the light from these planets is also refracted by Earth’s atmosphere.Besides, the size of a planet on the sky cancels out the turbulent effects of the atmosphere, hence a stable image is presented to the human’s eyes.

Illustration by Tom Callen of Cosmonova
Why stars twinkle, but planets don’t from EarthSky

However, we might see the planets twinkling if we see them lower in the sky. This phenomenon occurs because there are more turbulence effects and in the direction of any horizon, we are looking through more atmosphere compared when we look overhead.

Now, shall we continue with our song earlier?

Twinkle, twinkle, little star,
How I wonder what you are!
Up above the world so high,
Like a diamond in the sky.

Extra link for this song is available here (just kidding :P) :

EarthSky.org