Solar Prominences, August 26, 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. Even though the Sun has been very quiet this past year, with only a few inconspicuous sunspots, there are usually at least a few prominences to be seen every day. This prominence complex is about as tall as five Earths.
Astro Photography Home Page