Illustration of Sun's vibrational modes

This color picture is a computer representation of one of nearly ten million modes of sound wave oscillations of the Sun, showing receding regions in red tones and approaching regions in blue. By measuring the frequencies of many such modes and using theoretical models, solar astronomers can infer much about the internal structure and dynamics of the Sun. This technique is called helioseismology, because of its similarities to terrestrial seismology, and is at the heart of the NOAO program called the Global Oscillation Network Group (GONG). GONG operates an international network of instrument stations that provide continuous measurements of such oscillations, by always having a station in daylight at all times. This project will provide a greatly extended understanding of our nearest star.