# Stars: What makes them "twinkle?"

**URL:** <https://boards.straightdope.com/t/stars-what-makes-them-twinkle/300375>\
**Category:** Factual Questions\
**Created:** [April 21, 2005, 5:30am UTC](https://boards.straightdope.com/t/stars-what-makes-them-twinkle/300375 "2005-04-21T05:30:32Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![Amazon\_Floozy\_Goddess](https://avatars.discourse-cdn.com/v4/letter/a/779978/32.png) [@Amazon\_Floozy\_Goddess](https://boards.straightdope.com/u/Amazon_Floozy_Goddess)\
**Post date:** [April 21, 2005, 5:30am UTC](https://boards.straightdope.com/t/stars-what-makes-them-twinkle/300375/1 "2005-04-21T05:30:32Z")

</div>

I was looking at the stars tonight, and I noticed that every one of them twinkled. One of the planets was visible (I’m not sure which one), and that did not twinkle.

I know that our sun is a regular old star, and as far as I know I’ve never seen it twinkle (of course, one can’t really stare at it long enough to really tell).

What is it that makes stars twinkle, or is it an optical illusion?

…also, this is the first time I’ve ever said “twinkle” so many times at once.

---

<div class="post-metadata">

**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\
**Post date:** [April 21, 2005, 5:34am UTC](https://boards.straightdope.com/t/stars-what-makes-them-twinkle/300375/2 "2005-04-21T05:34:12Z")

</div>

It’s the air. Air currents and water vapor and whatnot smears the light a little bit, making stars look twinkly. In space, stars don’t twinkle.

---

<div class="post-metadata">

**Author:** ![Sublight](https://avatars.discourse-cdn.com/v4/letter/s/439d5e/32.png) [@Sublight](https://boards.straightdope.com/u/Sublight)\
**Post date:** [April 21, 2005, 5:46am UTC](https://boards.straightdope.com/t/stars-what-makes-them-twinkle/300375/3 "2005-04-21T05:46:18Z")

</div>

Twinkling only happens with points of light, which is what a star X light-years away essentially is. Planets, on the other hand, are close enough that they appear as disks in they sky (as does the sun), so they don’t twinkle.

---

<div class="post-metadata">

**Author:** ![Bag\_of\_Mostly\_Water](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bag_of_mostly_water/32/1029_2.png) [@Bag\_of\_Mostly\_Water](https://boards.straightdope.com/u/Bag_of_Mostly_Water)\
**Post date:** [April 21, 2005, 5:56am UTC](https://boards.straightdope.com/t/stars-what-makes-them-twinkle/300375/4 "2005-04-21T05:56:06Z")

</div>

[This](http://www.acme.com/jef/science_songs/twinkle-160.mp3) is probably the best explanation of why stars twinkle and planets don’t. (Warning – link is to a 2.2 MB mp3 file.)

---

<div class="post-metadata">

**Author:** ![rowrrbazzle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rowrrbazzle/32/414_2.png) [@rowrrbazzle](https://boards.straightdope.com/u/rowrrbazzle)\
**Post date:** [April 21, 2005, 9:02pm UTC](https://boards.straightdope.com/t/stars-what-makes-them-twinkle/300375/5 "2005-04-21T21:02:13Z")

</div>

There’s actually a second factor in twinkling. Because the light from an object takes a slightly different path to each of your eyes, its brightness will actually be at slightly different levels in each eye. You can see this by crossing your eyes slightly when looking at a star/planet.