Why do stars twinkle? And do stars actually twinkle?

ScienceAstronomy
Written By Caitlin Olson
 

The short answer

Stars do not actually twinkle – they only appear to twinkle! Stars appear to twinkle because the star's light is 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!).

​"Szintillation.Sirius" by Bautsch is licensed under CC0 1.0

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 don’t planets twinkle?

Planets don’t appear to twinkle because they 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/

 
Caitlin Olson

Caitlin is an amateur nerd who started Today You Should Know because she wanted an excuse to Google all the questions that have popped into my head. What Caitlin lacks in expertise, she makes up for in enthusiasm.

Have a question you’d like Caitlin to cover? Submit it using the link in the header.

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