Twinkling star formation
“Twinkle Twinkle little star,
How I wonder what you are.”
I am sure you have wondered about the “little star”, but have you wondered why it twinkles like a “diamond” in the sky?? The main reason for this is earth’s atmospheric turbulence.
As you all know, earth is made up of 6 main layers of atmosphere- troposphere, stratosphere, mesosphere, thermosphere, ionosphere and exosphere. These layers vary in their density and temperature. The constantly changing atmosphere will cause turbulence in the atmosphere. As each turbulent layer is of different composition, they can be considered to be a different medium. So, when light from a distant star reaches the earth’s atmosphere it gets refracted by each medium. Thus, the glittering diamonds you perceive is nothing, but the conglomerated refractions that the rays are forced to undergo, when it passes through each layer of the earth’s atmosphere. The amount of refraction or scattering will depend on the temperature of the scattering medium. If the air is warm or hot, the molecules will be further apart and hence will cause lesser scattering than when the air is cool.
The fact that the earth’s atmosphere is the cause for the “twinkling” is proved by Hubble space telescope, which has been installed in the outer space, free from the hurdles of the earth’s atmosphere. This telescope is known to produce crystal clear images of the entire Universe.
Stars like sun, which are near the horizon don’t twinkle. This is because the amount of radiations from the sun is very high, that the scattering of a few rays doesn’t matter much.
Hipparchus classified stars according to the amount of magnitude, ranging from one to six, first being the brightest. Scientists came up with methods such as photometry to quantify this brightness factor.
Planets, on the other hand, do not twinkle and are seen as discs through the telescope. As they are nearer to the earth, the atmospheric fluctuations and turbulence does not have any effect on the rays coming from these planets, and hence, the absence of twinkling.
