An ordinary planetary nebulae have one star at its center. A bipolar nebulae has a binary star system. The wings of the Twin Jet Nebula are thought to be caused by the motion of its two central stars around each other. As the dying main star and its white dwarf companion orbit around their common center of mass, the ejected gas from the dying star is pulled into the two lobes. The two stars at the heart of the nebula circle one another about every 100 years. This rotation not only forms the wings of the butterfly and the two jets, it also allows the white dwarf to strip gas from its larger companion which then forms a large disc of material around the stars extending out for billions of kilometers, up to 15 times the orbit of Pluto. Even though that disk is of huuge, it is still too small to be seen on the image taken by Hubble.
Image Credit: ESA / NASA