Helioseismology is the study of "sunquakes", the sound waves that propagate through the sun's interior and appear at its visible surface. As in terrestrial seismology, astronomers are now able to measure millions of sound waves that cause the Sun to vibrate or ring like a bell. Quentin Cooper finds out how scientists can measure the internal structure and sub-surface "weather" of the Sun by studying these waves.
Producer Fiona Roberts EMAIL: material.world@bbc.co.uk