Sun's oscillations. Computer model showing the effect of solar pulsations which cause the surface of the Sun to move in and out a few tens of metres. These pulsations are caused by sound waves which are generated within the solar convective zone, the outer layer of the Sun. Such vibrations are here visualised by using the Doppler effect; areas that are moving towards the Earth are blue and areas that are receding from the Earth are red. The model shows the effect of only one of the possible vibrations, also known as spherical harmonics. In reality millions of spherical harmonics combine together creating a more complex pattern on the Sun's surface.