This odd duo of a red giant and a white dwarf is called a symbiotic system. The red giant is also a Mira Variable, a pulsating red giant, that is far away from its partner. It could take as much as 100 years for the two to orbit around each other. Astronomers speculate that the interaction between these two stars may have sparked episodic outbursts of material, creating the gaseous bubbles that form the nebula. As a result, an accretion disk of material forms around the white dwarf and spirals onto its hot surface.
Gas continues to build up on the surface until it sparks an eruption, blowing material into space.
Dr. Sten Odenwald Return to Ask the Astronomer .