This is not a weird green nebula in the Milky Way Galaxy, but the skin on the rind of a seedless watermelon (Citrullus lanatus). Watermelon rinds can be eaten, and are pickled to overcome an unappealing flavor.
Equipment used: Canon EOS Rebel T5i with a standard zoom lens (EF-S 18-55 mm) on a 49 mm long extension tube.