Why do stars twinkle?

[warpig3]

Well, why do they? Some appear to twinkle yets some dont (are these non-twinkling ones planets?).

many thanks
warpig

[squarebear]

Yes the non twinkling ones are planets.

From what I remember from school, it's the Earth's atmosphere that distorts the rays of light from the stars making them twinkle.

[lilsecret]

http://curious.astro.cornell.edu/question.php? number=114

[warpig3]

Thanks SB, I was on the right tracks then.

[warpig3]

Excellent link lilsecret, many thanks.

[fo3nix]

Just to add: sometimes stars appear like crosses in photos. This is an artefact of the lens used to take the image.

[CT]

Stars appearing like crosses can also be an artefact of the struts holding the secondary mirror in the telescope.