Possible Duplicate:
Optical explanation of images of stars?
What are these rays that appear in photograph of sun?
I thought stars should look round shaped (similar to a sphere, or oblate spheroid) without extra tails nor should they twinkle as they were only caused by atmospheric distortion when seen from Earth. However I searched the web for some justification photos and I didn't find any. I found this photo from NASA which I expect was taken from space, that shows extra tails on the star
http://upload.wikimedia.org/wikipedia/commons/4/4e/Pleiades_large.jpg
Do you have any explanation?