As the name implies, this reflection nebula associated with the star Rigel looks suspiciously like a fairytale crone. Formally known as IC 2118 in the constellation Orion, the Witch Head Nebula glows primarily by light reflected from the star. The color of this very blue nebula is caused not only by blue color of its star, but also because the dust grains reflect blue light more efficiently than red. A similar physical process causes Earth's daytime sky to appear blue.
Image Credit: NASA/STScI Digitized Sky Survey/Noel Carboni
Explanation from: https://www.nasa.gov/multimedia/imagegallery/image_feature_1209.html
Arsalan
Tuesday, October 31, 2017