Stars often twinkle because of turbulence on Earth’s atmosphere. A star is essentially a point of light as seen in the sky, so its beam is easily distorted and can appear to move around or be broken up, often into colours. This behaviour is attractive when seen with the naked eye, but something of a disaster when you are trying to make observations through a telescope, though for sheer spectacle the view of a bright star such as Sirius madly twinkling can be fun to watch. Stars twinkle less when they are high in the sky, and planets twinkle much less because they are not points of light but have discs, even though they might not be visible to the naked eye. Twinkling is strongly linked with poor seeing, and is usually worse when the jet stream is overhead. It is less during stable weather conditions, such as high pressure, when there may be hardly any twinkling. As seen from space, the stars don’t twinkle at all.
