SOHO spacecraft helps to uncover workings of sunspots
The ESA (European Space Agency)-NASA SOHO spacecraft has discovered that sunspots, dark patches on the Sun visible from Earth, are caused by whirlpools of gas near the Sun's surface where hot gas flows converge and dive towards the centre at speeds of up to 4000 kilometres per hour. Sunspots are visible as they strangle the normal up-flow of energy from the Sun's interior and leave the area cooler and darker than its surroundings. The converging flows of gas identified around sunspots explain the concentration of magnetic activity they bring about, often associated with solar flares and other phenomena which affect space weather and the Earth itself. The Sun's activity peaks roughly every 11 years, with the latest maximum sunspot count occurring in 2000. ESA's SOHO project scientist Bernhard Fleck said: 'The origin and stability of sunspots has been one of the longstanding mysteries in solar physics. I am delighted to see that with SOHO we are beginning to crack this problem.' The gas flows surrounding sunspots were detected by a team of scientists in the USA using SOHO's Michelson Doppler Imager (MDI). The instrument explores the Sun's interior by detecting natural sound waves at a million designated points on its surface. 'After many years of contradictory theories about sunspots, MDI on SOHO is at last telling us what really happens,' said Junwei Zhao of Stanford University, California. SOHO is a cooperative project between the ESA and NASA. The spacecraft was built in Europe for ESA and equipped with instruments by teams of scientists in Europe and the USA. NASA launched SOHO in December 1995, and in 1998 ESA agreed to extend its operations until 2003.