SOHO - listening to the Sun's song

The Solar and Heliospheric Observatory (SOHO) is a project of international cooperation between ESA and NASA to study the Sun, from its deep core to the outer corona, the solar wind, and its interaction with the interstellar medium. A consortium of European space companies built SOHO under overall management by ESA, and twelve international consortia developed its suite of instruments. SOHO is operated from NASA Goddard Space Flight Center in Greenbelt, Maryland. SOHO moves around the Sun in step with the Earth, by slowly orbiting around the First Lagrangian Point (L1), where the combined gravity of the Earth and Sun keep SOHO in an orbit locked to the Earth-Sun line. The L1 point is approximately 1.5 million kilometres away from Earth (about four times the distance of the Moon), in the direction of the Sun. There, SOHO enjoys an uninterrupted view of our daylight star.

Visible light, UV and EUV telescopes measure magnetic fields, temperatures, densities, flows and dynamic phenomena such as flares and coronal mass ejections in the Sun's atmosphere. Other instruments record the energy distribution and chemical composition of the solar wind and energetic particles. Three instruments listen to the "Song of the Sun". The entire Sun vibrates from a complex pattern of acoustical waves, much like a bell. By tracking and deciphering these sound waves - a technique called "helioseismology" - scientists can learn about the complex interior of our daylight star.

Detail from SOHO/EIT 195 image (Extreme-ultraviolet Imaging Telescope with 195 Angström filter)

latest EIT171 (blue), EIT184 (yellow), EIT304 (red) and MDI