Why do stars twinkle and planets do not class 10?

When you look at the sky at night, what do you see? Two things every person would see is the moon and the stars. You know the moon is just an astronomical body that orbits the earth as the only natural satellite. You will see a lot of stars in the sky at night but they are very far away from earth. Even if you saw the stars with the help of a large telescope then you will see it as a pinpoint image. These pinpoint images that you see are because they twinkle at night and our naked eyes catch that twinkle point not the star. 

How do stars twinkle?

The main reason for stars twinkling is because of the refraction of lights. When the light of the stars enters the atmosphere of the Earth, it gets refracted or we can say bend into different directions because of the different atmospheric layers. Also when they enter the Earth’s atmosphere, the change in the direction and speed of the wind and the temperature change refracts the light. 

A ray of light always bends when it travels from one medium to another. And this bending of light is known as refraction. Refraction plays a very important role in the twinkle of stars. If the ray of light travels from dense medium to rare medium then it bends away from normal. If the ray of light travels from rarer medium to dense, then it bends towards the normal. 

The atmosphere of the Earth is made up of different layers, so when the light from the stars enters the atmosphere then it shatters because of the speed of the wind and the change on temperature, thus the density is changed. So when a ray of light reaches us directly and when some of it bends away, it gives us the twinkling effect of the star. 

Why do planets not twinkle?

Planets appear as disks because they are closer to the Earth. When you see the planet through a big telescope then they will also be seen as a disk while stars will be seen as a pinpoint. When the light from the planet travels through the Earth’s atmosphere, it also bends because of the change in the wind, density, and temperature of the Earth’s atmosphere. So when the light appears on the Earth, then we see it as a shining object rather than a twinkling effect. It is because of the distance and the lack of refraction. So that’s why planets shine rather than twinkling. 

If we see stars and planets from outer space then we notice that they both shine. The reason behind this is there will be no atmosphere to disturb the ray of light and when the light doesn’t refract then you will see that they both shine rather than twinkle. These kinds of experiments are done in school with the help of a glass prism to see and notice the refraction of light. 


So, we can conclude that with the help of refraction, stars appear to twinkle. And planets shine because of the lack of refraction in the light coming from the origin to Earth. Even if you see these objects from the telescope, then you will also notice that stars will appear as pinpoint objects and planets will appear as a disk kind of image. 

FAQs on why do stars twinkle and planets do not class 10

  1. How many constellations can be seen from naked eyes?

Answer. Constellations are a group of stars that form a shape or pattern in the sky. They can be seen from the naked eyes. In the darkest night, we can see approx 80 constellations from the naked eyes. 

  1. What are the causes of the refraction of light?

Answer. The causes of refraction of light are the density, wind speed, and temperature which makes the light bends when it came from the stars and enters the Earth’s atmosphere. 

  1. What are the major constellations of stars?

Answer. Constellation can be seen through naked eyes and it seems beautiful when the stars form a pattern and shape and twinkle. So, here are the major constellations of stars: 

  • Ursa Major- The great bear 
  • Ursa Minor- The little bear 
  • Orion- The Hunter
  • Taurus- The Bull
  • Gemini- The Twins 

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