On August 24th and 25th, the STEREO Ahead spacecraft observed an enormous filament on the southeastern edge of sun expand into a huge prominence. The images were recorded with the Extreme Ultraviolet Imager (EUVI) in the 304 Angstrom wavelength. The prominence expanded 100s of thousands of kilometers above the solar surface creating a loop of hot plasma. That would be about 45 earths stacked end-to-end. The hot plasma is material from the sun’s chromosphere with a temperature of around 20,000 Kelvin. The prominence supported by magnetic fields expands high above the solar surface over a period of 30 hours. Some of the material escapes the sun’s gravity while most of it falls back to the surface. The part of the prominence that escaped into space was directed well away from earth. The terms prominence and filament are really referring to the same type of object. The distinction is historical with filament referring to the material when observed with the solar disk in the background and prominence referring to it when space is in the background. Also note that on the sun east and west are backwards from earth with east on the left and west on the right. This is because the sun rises or rotates into our field-of-view from the left. So when looking at the sun it still “rises” from the east.
About C. Alex Young, Ph.D.
