Filaments of glowing gas that one can imagine to be shaped like a jellyfish, suggests this nebula’s popular name, The Medusa Nebula. Also known as Abell 21, this Medusa is an old planetary nebula some 1,500 light-years away in the constellation Gemini. The nebula is associated with a dramatic transformation. The planetary nebula phase represents a final stage in the evolution of low mass stars like the sun as they transform themselves from red giants to hot white dwarf stars and in the process shrug off their outer layers. Ultraviolet radiation from the hot star powers the nebular glow. The Medusa’s transforming star is the faint one near the center of the overall bright crescent shape. In this telescopic view, fainter filaments clearly extend to the right of and below the bright crescent region. The Medusa Nebula is estimated to be over 4 light-years across.

You may notice some nebulosity to the left-bottom of this shot. That’s actually rays coming from a closeby bright star whose bright rays somehow leaked into this image.

I took this image over 18 hours (41 images of Luminance of 20 minutes and 9 images of RGB colors of 10 minutes each.)