IC 2118, the Witch Head Nebula glows primarily by light reflected from Rigel. Rigel is located about one photo-width off the image to the right. Fine dust in the nebula reflects the light. The blue color is caused not only by Rigel's blue color but because the dust grains reflect blue light more efficiently than red. The same physical process causes Earth's daytime sky to appear blue, although the scatterers here are molecules of nitrogen and oxygen. The nebula lies about 1000 light-years away.
This image was selected for the Astronomy Picture Of the Day, Feb. 27, 2001, was Santa Barbara Instrument Group's "Image of the Month" for January, 2001 and was published in Sky and Telescope Magazine, May 2001 issue, pages 141 & 143.
Taken by Gary with a Takahashi FSQ-106N 4-element fluorite refractor at f/5. See equipment and imaging details for this shot.