Comet or Nebula?

Source: http://apod.nasa.gov/apod/ap100826.html

NEBULA

During the 18th century in France, Astronomer Charles Messier routinely hunted for comets, keeping a list of those who were in fact not comets. Messier 27 or M27 is a perfect example, not a comet nor a planet, M27 is classified as a gaseous emission nebula. M27 dubbed the Dumbbell Nebula is over 2.5 light-years across and about 1,200 light-years away in the constellation Vulpecula.

The Nebula was created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star's outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star's intense but invisible ultraviolet light.