Why Stars Twinkle

When I was a child, I was a very curious little tyke. I was always asking questions about everything, especially about nature. When the fall of the year arrived, it amazed me how the leaves on the trees knew it was time to fall off. In the spring, I was amazed how the flowers knew it was time to blossom. When I saw ant hills, I wondered why the ants needed to make little dirt hills. I was struck with awe and wonderment as I gazed up at the dark night sky, watching all those beautiful twinkling little stars as if they were putting on a show for me.

It wasn’t too long before I was gazing up at the night sky with a telescope.When I was about thirteen years old, a neighborhood friend of mine, Greg, got a telescope for Christmas. He set it up in his back yard and we focused it on the moon. We stood there for hours just looking at the different craters. This really made a big impression on me.

One particular night as we were looking at the moon I said I wanted to look at other things. It was easy to distinguish between the planets and the stars as the stars were the pin-point lights that were always twinkling, and the planets didn’t twinkle. We knew this from the little booklet that came with the scope. At that point, my curiosity was really piqued. I couldn’t help but wonder why the stars twinkled and not the planets.

At that time, I didn’t make an honest effort to find out why the stars twinkled. I just accepted the fact that they naturally twinkled because I thought they were made up of different gases which made the twinkling phenomenon occur. It wasn’t until I took my first college astronomy class that I found out the real reason why stars twinkled.

First, scientists don’t say “stars twinkle.” They use a much more scientific term. They call it astronomical scintillation. Now for the good part, why do stars twinkle? The answer is quite simple. The light from the star is scattered as it reaches the earth’s atmosphere. This is due to the variations in air temperature. As the light encounters warm air, it is scattered less. Warm air molecules are spread further apart, therefore there is less scattering of light. As the light encounters cool air, it is scattered more. This back and forth turbulent flow of warm and cool air makes the light coming from the star appear to be twinkling. This easily happens due to the fact that a star is so far away, that only one ray of light reaches the earth. It is easier for one ray of light to be scattered as opposed to many rays of light. This is why the moon or a planet doesn’t appear to be twinkling. They are much closer to the earth with more rays of unscattered light hitting our eyes, making them appear as a steady light.

So remember this, as you gaze up into the dark night sky and see all those little twinkling stars just twinkling away, you are actually seeing scattered light being bounced off the earth’s atmosphere. Even though this is the case, it still doesn’t take away the beauty and the wonderment of all those tiny little diamonds just sparkling away against the dark night sky. Remember? “Twinkle, twinkle, little star, how I wonder what you are. Up above the world so high, like a diamond in the sky.”