Today the ESA/NASA SOHO satellite captured this image of a huge spectacular eruptive prominence escaping the Sun. Prominences are loops of magnetic fields with hot gas trapped inside. Sometimes, as the fields become unstable, the they will erupt and rise off of the Sun in just a few minutes or hours. If eruptions like these are directed toward the Earth they can cause a significant amount of aurora and other geomagnetic activity.
Image taken 2002 July 1 13:19 UT
This images is taken by the EIT instrument on SOHO in the resonance line of singly ionized helium (He II) at 304 Angstroms in the extreme ultraviolet. The material in the eruptive prominence is at temperatures of 60,000 - 80,000 K, much cooler than the surrounding corona, which is typically at temperatures above 1 million K.
The eruption can soon be followed as it moves out in space by looking at the SOHO LASCO images on our real-time image page where images are updated every 15 minute or so.
Wondering how big these events are relative to the earth? http://umbra.nascom.nasa.gov/eit/images/Sun_and_earth.jpg
Other nice prominence shots and movies from SOHO http://soho.nascom.nasa.gov/hotshots/2000_01_08/