Caption: This EIT full sun image, taken on 14 September 1999 in the He II emission line at 304 A shows the upper chromosphere/lower transition region at a temperature of about 60,000 K. The bright features are called active regions. A huge erupting prominence escaping the Sun can be seen in the upper right part of the image. Prominences are "cool" 60,000 K plasma embedded in the much hotter surrounding corona, which is typically at temperatures above 1 million K. If an eruption like this is directed toward the Earth it can cause a significant amount of geomagnetic activity in the Earth's environment with a following spectacular aurora.
Instrument: EIT (Extreme ultraviolet Imaging Telescope);
Taken: Sept 14 1999, 07:19UT