Why do Stars Twinkle?

Most of us remember the childhood song about the stars twinkling in the sky. We may have actually wondered what they were. But did we try to figure out just why stars twinkle?

Only a few people have gone on to study stars in sufficient detail to try and determine why they seem to twinkle in the night sky. While this may seem like it requires a complex answer the truth is rather simple. Stars seem to twinkle because we are seeing them from Earth through several layers of moving air. While the night sky may seem very still and peaceful there is a lot of movement in the Earth’s atmosphere.

Light generally travels in a straight line, or at least it appears to when we see it with our human eyes. In fact, light will travel in a relatively straight path unless that path is interrupted by something – such as the atmosphere. The light leaves the star millions of miles away and goes straight until it comes into contact with a pocket of air that is denser or has a different temperature.

These changes happen so quickly the changes in light levels seem like twinkling. Measurements will show that stars closer to our horizon will seem to twinkle more because they have to travel through more of the atmosphere than stars overhead. If the stars were close enough to appear very large we wouldn’t notice the twinkling. This is the case with planets that appear in our night sky but don’t twinkle as the distant stars do.

Space Traveler

If we were able to travel in space and get through the Earth’s atmosphere we would still be seeing stars that are millions of miles away. However, those stars wouldn’t appear to twinkle because we would have traveled through the atmosphere. There would be fewer differences in the air density and temperature to change the light’s direction.

We might also be more aware of the twinkling phenomenon when we return to Earth. We might see those distant stars twinkling but may also notice that the Moon doesn’t twinkle, even on the brightest night. The Moon’s surface is lit at an angle by the sun and it is much too close to Earth to produce the twinkling sensation.

In recent years scientists have developed a theory stating that certain gas clouds in our solar system are responsible for twinkling. Celestial objects that are very close to Earth may be inside the gaseous region and may not twinkle even if they are seen from sufficient distance.

Some scientists and astronauts who brought back information from space are convinced that the Earth’s atmosphere causes the twinkling of stars. They say it doesn’t have anything to do with clouds of gas. The best information we have to date supports the Earth’s atmosphere theory.

But there’s nothing to keep explorers and scientists from discovering new causes for a phenomenon such as the twinkling of stars.