Filaments Across the Sun . ... Credit Copyright: Greg Piepol (sungazer.net) Explanation: Two unusually long filaments crossed part of the Sun last week. The filaments are actually relatively cool and dark prominences of solar plasma held up by the Sun's magnetic field but seen against the face of the Sun . ... The above image was taken early last week through a small telescope in a very specific color of light emitted primarily by hydrogen . ... NASA Official: Jay Norris. ...