Solar Prominence, May 24, 2008. This photograph was taken with a hydrogen alpha scope that only shows one wavelength of light, at 656.3 nanometres. This is the particular wavelength of hydrogen alpha light. Observing the Sun in hydrogen alpha makes it possible to see structural details.
Large prominences of plasma lift off the surface of the Sun at tremendous speeds, and they are most easily seen along the edge with the darkness of space behind them. They can change their shape quickly, and I watched this one develop during the course of the day. This photograph was taken at 19:40 UT. Prominences follow powerful magnetic fields generated by the Sun. The Earth would be less than one quarter the height of this prominence.
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