Solar prominence. Ultraviolet SOHO (Solar and Heliospheric Observatory) satellite image of a solar prominence (top right). The prominence is erupting from the chromosphere (orange), which lies above the Sun's visible surface, the photosp- here. Prominences are dense clouds of plasma, or ionised gas, in the Sun's outer layer, the corona. They are typically at temperatures of 60,000 Kelvin, much cooler than the several million Kelvin of the corona. Active regions (white) mark areas of high solar activity. The Sun's activity peaks every 10-11 years. Image produced by SOHO's Extreme Ultraviolet Imaging Telescope (EIT) on 14 September 1999, as the Sun approached such a time.