What do complex, asymmetric structures observed in planetary nebulae often suggest about the star's final stages?

Answer

Evidence of episodic events or interactions with a companion star.

While a steady wind creates a spherical nebula, the presence of asymmetries, clumps, or bipolar shapes is interpreted as evidence for episodic events, strong flares, or external interactions occurring during the star's unstable closing stages.

What do complex, asymmetric structures observed in planetary nebulae often suggest about the star's final stages?
starradiationmassevidencestellar wind