2001A&A...376..484J

New, high-sensitivity interferometric CO observations of BV 5-1 show that the molecular gas in this bipolar planetary nebula is distributed along a very inhomogeneous ring made of clumps. The individual masses of such molecular clumps are ∼10^–4M_☉. The BV 5-1 molecular ring is seen edge-on, it is nearly perpendicular to the axis of bipolarity of the nebula, and it is expanding with an expansion velocity of ∼9km/s. BV 5-1 is confirmed to be a relatively evolved nebula, as indicated by both its kinematic age (∼2.4x10⁴yrs) and its molecular to ionized mass ratio (∼0.3). The structure of the BV 5-1 molecular ring, as well as that of other rings previously observed in a few additional nebulae, underscore the importance of strongly asymmetrical mass loss processes starting early at the asymptotic giant branch phase.