Astronomers estimate that there are between one hundred and four hundred billion stars in our galaxy¹. When you look at them with the naked eye, they twinkle, but you may be surprised to learn that the twinkling is an illusion!
The air around us causes this illusion. Earth’s atmosphere is never still. Cold air falls, and warm air rises. As a result, light can be bent by these temperature variations ².
Think about it this way: A star is like a spaghetti noodle, and the atmosphere is like a pasta strainer. The noodle only wiggles after it is hot and cooked, like a star only shimmers after its light passes through the atmosphere. Stars do not twinkle in outer space.
Planets also shine like stars. Telling the difference between the two can be hard sometimes. If you are ever confused, remember that planets do not twinkle but stars do. Another difference is that a star creates its own light, but a planet’s light is reflected3.
The next time you see the stars, remember that our atmosphere’s varying temperature creates the twinkling we see! Regardless of how hot or cold the air temperature is, there will always be quite a show in the night sky.
Try this optical illusion – do you see the dots changing between black and white?
* This article has been updated to reflect ongoing advances in scientific knowledge. It was originally published in Zealousness 15.
- Howell, Elizabeth, “How Many Stars Are in the Milky Way,” SPACE.com, last updated February 11, 2022, https://www.space.com/25959-how-many-stars-are-in-the-milky-way.html
- Todd, Iain, “Why do Stars Twinkle but Planets Don’t,” March 3, 2021, https://www.skyatnightmagazine.com/space-science/why-do-stars-twinkle