Stars — do they really twinkle?

Twinkle, twinkle, little star… We have all heard or sang this song as a kid. But is the song actually based on facts? Do stars really twinkle or is it just an illusion? 

What is a Star?

According to the Cambridge English Dictionary, a star is “a very large ball of burning gas in space that is usually seen from the earth as a point of light in the sky at night. Stars are just huge celestial bodies of helium and hydrogen that emits light and heat due to the movement of its nucleus. Stars contain plasma and are held together due to gravity. NASA estimates that there are over 100 billion stars in our galaxy alone, the Milky Way.

Do They Really Twinkle?

For you to really understand the answer to this question, you need to know why stars shine in the first place…

Stars shine due to the immense pressure of gravity holding them together. This pressure causes the nucleus (or the core) of the star to heat up and start the process of nuclear fusion. Nuclear fusion is the process of combining two atomic nuclei and forming a single and bigger one. When this process happens inside a star, it combines hydrogen nuclei and forms various isotopes, eventually graduating to alpha particles (helium nuclei). Because of relativistic mass-energy equivalence, this generates energy when gluon bonds break! Just like a campfire, the hotter the stars get, the stronger it will shine!

This raises the question “do stars really twinkle?”

In short, stars actually don’t twinkle. The twinkling that we see is merely an illusion. Stars appear to twinkle because as light enters the earth’s atmosphere the light is bent and distorted due to winds, temperature, and density of the air. Additionally, a lot of visible stars are really far away, meaning that objects in space can block our view of them. This effect is only seen from earth. For example, if we go up close to the stars they in fact don’t twinkle, they just glow.

Why do Some Glow in Different Colors?

Stars are classified by a number of different factors. The glow of a star can vary due to temperature and distance from earth. The closer a star is to Earth, the brighter it will appear to us. The farther a star is, the dimmer we will see it.

Sometimes, we see stars that appear to shine in colors. This is due to the temperature of a star. The coldest stars usually have a red-brown color. Hot stars, on the other hand, shine in a blue color. Our sun is in the middle temperature zone, not the hottest; but not the coldest. Hence, it shines in a yellow to white color.

The next time you look up the sky and find a twinkling star, remember why they seem to twinkle and the wonders that stars possesses.

Featured image from: Vadim Sadovski/


Sarah Okalani

A girl who wants to make a difference in the world 🌎

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