The new nebula in my list of favorites – The Calabash Nebula – known commonly as The Rotten Egg Nebulae not because it resembles one but because it smells like one – :p well, at least that is what we expect due to the unexpectedly large amount of Sulfur in it!
This is a proto-planetary nebula (PPN) located ~ 5000 light years from us, surrounding a cool and dying star. It is a field of violent gas collisions resulting in supersonic shock fronts. Material ejected from the central star are accelerated in opposite directions which form the densest regions in the nebula (seen as yellow). The dusty part at the center of this bipolar structure is hiding the dying star which is creating this beautiful structure in space!