Pairs of Bubbles in Planetary Nebulae and Clusters of Galaxies

I point to an interesting similarity in the morphology and some nondimensional quantities between pairs of X-ray-deficient bubbles in clusters of galaxies and pairs of optical-deficient bubbles in planetary nebulae (PNs). This similarity leads me to postulate a similar formation mechanism. This postulate is used to strengthen models for PN shaping by jets (or collimated fast winds [CFWs]). The presence of dense material in the equatorial plane observed in the two classes of bubbles constrains the jets and CFW activity in PNs to occur while the asymptotic giant branch star still blows its dense wind, or very shortly after. I argue that only a stellar companion can account for such jets and CFWs.