Twinkling

Twinkling consists of changes in the apparent brightness and position of stars caused by atmospheric turbulence and various other irregularities. In photographs, twinkling causes an image to be "smeared" into a "seeing disk". The effects of twinkling can be, partially, corrected for by active and adaptive optics. Twinkling is the subject of the song Twinkle, Twinkle, Little Star (1761).