Twinkling Lights

Written by: Paige Leal

Have you ever looked up at the night sky and noticed how some stars look as if they are sparkling or and flickering? Even though stars look like tiny blinking lights from Earth, they are actually producing a steady amount of light. The reason they appear to twinkle has more to do with Earth’s atmosphere than with the stars themselves.

As starlight travels millions of miles through space, it moves in a straight line without much interference. The starlight's journey is not always that simple though, because once in Earth's atmosphere, things change. The atmosphere is made up of layers of air with different temperatures and densities. These layers are constantly moving because of wind and changes in weather. When light from a star passes through them, the light bends slightly in different directions. This bending of light is called refraction.

Since the atmosphere is always shifting, the starlight keeps changing direction before it reaches our eyes. Sometimes the light appears brighter, and other times it appears dimmer. This constant change is what makes stars seem to twinkle or shimmer in the sky. The effect is stronger when the atmosphere is more turbulent, such as on windy nights.

Stars twinkle more than planets because stars are so far away from Earth that they appear as tiny points of light. Planets are much closer and appear slightly larger in the sky. Their light spreads out more, so the atmosphere does not distort it as dramatically. That is why planets usually shine more steadily, and don’t produce a “twinkle” effect.

The amount of twinkling can also depend on where a star is located in the sky. Stars closer to the horizon often twinkle more because their light has to travel through a thicker layer of Earth’s atmosphere before reaching us. Stars directly overhead usually appear steadier since their light passes through less air.

So, the effect of these twinkling stars is really caused by complicated movements in Earth’s atmosphere. The next time you look up at the night sky, the sparkling lights above you will be a reminder that even Earth’s air can change the way we see the universe and the journey stars go through to be seen.