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The Butterfly Nebula has quite a few other names: Minkowski 2-9, M2-9, Minkowski’s Butterfly, the Wings of a Butterfly Nebula, and Twin Jet Nebula. It is a planetary nebula discovered by Rudolph Minkowski. The nebula is located about 2,100 light years from Earth. This is a bipolar nebula that has twin lobes emanating from a central star.
The Butterfly Nebula is actually the result of the impending death of the binary star system at the nebula’s center. The primary component is the hot core of a star that reached the end of its main-sequence life cycle then ejected most of its outer layers and became a red giant(this will happen to our Sun in about 5 billion years). The star is now contracting into a white dwarf. Astronomers believe that it was a sun-like star early in its life. The secondary star is in close orbit. Possibly, the secondary was engulfed by the expansion of the primary. The interaction of the two star’s could have caused the formation of the nebula. Scientists think that the stronger gravity of one star pulls gas from the weaker star and projects it into space, which would explain the appearance of M2-9. The size of the nebula has dramatically increased because wickedly fast stellar wind that blows into the disk. Despite the nebula’s spectacular appearance, the outer shell is estimated to be a mere 1,200 years old.
It might help to understand some of the underlying terminology. A planetary nebula is an emission nebula(a cloud of ionized gas that emits light of various colors) consisting of an expanding glowing shell of ionized gas that is being ejected during the asymptotic giant branch(low to medium mass stars) phase near the end of certain star’s lives. They are a relatively short-lived phenomenon, lasting only tens of thousands of years. At the end of the star’s life(red giant phase) the outer layers of the star are expelled by pulsations and stellar winds. The hot, luminous core emits ultraviolet radiation that ionizes the ejected material and the energized material radiates as a planetary nebula. A bipolar nebula is simply a planetary nebula that is radiating in two directions and the material appears to be symmetrical.
No matter how you describe it, the Butterfly Nebula is quite spectacular to observe. Look in the direction of the constellation Ophiuchus to see what I mean.
We have written many articles about the Butterfly nebula for Universe Today. Here’s an article about the new Hubble images of the Butterfly nebula, and here’s an article about the explosive history of Eta Car.