2008ApJ...675L.101E

As stars evolve along the asymptotic giant branch (AGB), strong winds are driven from the outer envelope. These winds form a shell, which may ultimately become a planetary nebula. Many planetary nebulae are highly asymmetric, hinting at the presence of a binary companion. Some post-AGB objects are surrounded by tori of crystalline dust, but there is no generally accepted mechanism for annealing the amorphous grains in the wind to crystals. Here, we show that the shaping of an AGB wind by a binary companion provides a possible mechanism for forming crystalline dust in the orbital plane.