Animation showing far-side imaging of the Sun

The Sun is filled with many kinds of sound waves caused by the boiling motion of gas in its surface layers. SOHO’s Michelson Doppler Imager (MDI) instrument traces these ‘sound waves’ reverberating through the Sun to build up a picture of the far side. The MDI uses a far-side imaging method which compares the sound waves that emanate from each small region on the far side, with what was expected to arrive at that small region from waves that originated on the front side.