Why do stars twinkle?

If you've ever watched the stars at night they twinkle.

The famous nursey rhyme, "Twinkle, twinkle little star" is based upon  this very observation.

If however, you travel to the moon and observe the stars from there they would not twinkle.

Why do stars twinkle on Earth, but not on the moon? Any guesses?


 Stars twinkle on Earth because the atmosphere consists of moving pockets of warm and cold air.

These pockets of air have different densities which bend the light in various directions. This creates a twinkle.

On the moon to here is no atmosphere or air to distort the light. Stars seen from the moon therefore, should not twinkle.


Did you know that?

  • Stars change colour on twinkling. eg. from blue, red and yellow. This happens because the light from stars is composed of different colours which are bent in various directions by the atmosphere. See image above. This is why stars change colour on twinkling. 
  • Stars twinkle more near the horizon because there is a lot more air or atmosphere in this direction then directly above us.
  • Planets do not twinkle. The light from stars comes to us as a single point source. The reflected light from a planet comes from numerous points in the sky due to the planets close distance. Any bending caused by atmospheric disturbances are averaged out. This produces a relatively clear image.
  • The Hubble telescope has taken some very clear pictures of stars because there is no atmopshere in outer space to distort the image. 
  • The scientific term used to explain why stars twinkle is called "stellar scintillation"


Twinkle, Twinkle Little Star, played by Robot

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