Why do some stars appear to twinkle?
📓 The short answer
Stars do not actually twinkle — they only appear to twinkle! The visual effect is caused by the star’s light passing through the heat fluctuations in our atmosphere.
📚 The long answer
Get ready for some scintillating knowledge! 👀
Have you ever noticed how you can “see” heat radiating off asphalt on a hot day? As light passes through the hot and cool air above the road, the varying temperatures cause the light waves to change in speed and direction. In other words, the speed of light is dependent on the physical conditions of the substance it is passing through!
When we are looking at a night sky, we are seeing some stars twinkle because their light is passing through the varying temperatures of our atmosphere. Astronomers have a fancy name for stars twinkling — atmospheric scintillation (I told you to get ready for something scintillating!).
Atmospheric scintillation — while the subject of nursery rhymes and a nice thing to look at on a clear night — is an annoyance for astronomers! The wiggles make it difficult to keep stars in their telescope images.
🧠 Bonus brain points
What about other planets? Why don’t they appear to twinkle?
The reason is because planets are much closer to us than stars. Since the distance that a planet’s light has to travel to Earth is much shorter than a star’s light, there is less opportunity for the light to be impacted by the varying temperatures in our atmosphere.
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Sources
- Brhel, J. (2016, May 19). Why Do We See Waves on Hot Objects? Press & Sun-Bulletin. Retrieved October 2, 2022, from
https://www.pressconnects.com/story/news/local/2016/05/19/why-do-we-see-waves-hot-objects/84598570/ - Byrd, D. (2018, November 23). Why Do Stars Twinkle, but Planets Don’t? EarthSky. Retrieved October 2, 2022, from https://earthsky.org/space/why-dont-planets-twinkle-as-stars-do/
- Todd, I. (2021, March 23). Why Do Stars Twinkle? BBC Sky at Night Magazine. Retrieved October 2, 2022, from https://www.skyatnightmagazine.com/space-science/why-do-stars-twinkle/
