When asymmetric cosmic bubbles betray a difficult marriage: the study of
  binary central stars of Planetary Nebulae
  Planetary Nebulae represent a powerful window into the evolution of
low-intermediate mass stars that have undergone extensive mass-loss. The nebula
manifests itself in an extremely wide variety of shapes, but exactly how the
mass lost is shaped into such a diverse range of morphologies is still highly
uncertain despite over thirty years of vigorous debate. Binaries have long been
thought to offer a solution to this vexing problem. Now, thanks to recent
surveys and improved observing strategies, it appears clearly that a binary
channel, in particular common-envelope (CE) evolution, is responsible for a
large fraction of planetary nebulae. Moreover, as planetary nebulae are just
"fresh out of the oven" compared to other post-CE systems, they provide
invaluable contributions to the study of common-envelope evolution and to the
formation of jets in binary systems. Our studies have also started to identify
strong links between binarity and morphology, including a high proportion of
bipolar nebulae and rings of low ionisation filaments resembling SN 1987A.
Equally important are the newly found binary CSPN with intermediate periods,
which appear linked to chemically peculiar stars whose composition was modified
by binary evolution. Their study may also reveal much information on mass and
angular momentum transfer processes in binary stars. Here we show examples of
four PNe for which we have discovered their binary nature, including the
discovery of a rare case of a barium-rich cool central star.
