M27: Not A Comet

While searching the skies above 18th century France for comets, astronomer Charles Messier
diligently recorded this object as number 27 on his list of things which are definitely not
comets. So what is it? Well, 20th century astronomers would classify it as a Planetary
Nebula ... but it's not a planet either, even though it may appear round and planet-like in
a small telescope. Messier 27 (M27) is now known to be an excellent example of a gaseous
emission nebula 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. Known by the
popular name of the Dumbbell Nebula, the beautifully symmetric interstellar gas cloud is
about 1,200 light-years away in the constellation Vulpecula. This intriguing color composite
view was recorded through narrow band filters sensitive to emission from hydrogen atoms
(shown in red) and oxygen atoms (shown in blue/green).