Wings of a Butterfly Nebula
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The Wings of a Butterfly Nebula (M2-9 and also known as the Twin Jet Nebula) is about 2,100 light-years away from Earth in the direction of the constellation Monoceros. It represents the spectacular "last gasp" of a binary star system at the nebula's center. One component of this binary is the hot core of a star that reached the end of its main-sequence life cycle, ejected most of its outer layers and became a red giant, and is now contracting into a white dwarf. This central star is one of a very closely orbiting pair - the smaller star may even have been engulfed by the other's expanding stellar atmosphere.
The resulting interaction has created the stunning planetary nebula. Astronomers theorize that the gravity of one star pulls some of the gas from the surface of the other and flings it into a thin, dense disk extending into space. Such a disk can successfully account for the jet-exhaust-like appearance of M2-9.
The nebula has inflated dramatically due to a fast stellar wind, blowing out into the surrounding disk and inflating the large, wispy hourglass-shaped wings perpendicular to the disk. These wings produce the butterfly appearance when seen in projection. The total diameter of the nebula is about one-third of a light-year, or 2 trillion miles.
Early in its life the main component of the system was believed to be a sun-like star.