The Sun, by SOHO

Credit: SOHO (ESA & NASA)

A number of spacecraft observe our Sun. One mission, which has been in operation for almost a dozen years now, is the Solar & Heliospheric Observatory (SOHO). Launched on December 2, 1995 and beginning operations in May 1996, SOHO is a joint collaboration between the European Space Agency and NASA to study the Sun from the core to the outer corona and the solar wind. SOHO is also the primary provider for near-real time data of the Sun's activities, which allows astronomers to forecast space weather.

One of the instruments aboard SOHO is the Extreme Ultraviolet Imaging Telescope or EIT. The EIT studies the lower corona and the transition region between the chromosphere and the corona by taking full disc images of the Sun at four selected wavelengths in the extreme ultraviolet. These wavelengths correspond to temperatures between 80,000 and 2,500,000°C.

The above image is a composite of three separate images, taken in May 1998, at 171Å (Angstrom; the blue image), 195Å (green) and 284Å (yellow). Each wavelength reveals solar features unique to that wavelength. Since the EIT images come from the spacecraft in black and white, they are color coded for easy identification.