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Our Cycle 0 ALMA observations confirmed that the Boomerang Nebula is thecoldest known object in the Universe, with a massive high-speed outflow thathas cooled significantly below the cosmic background temperature. Our new CO1-0 data reveal heretofore unseen distant regions of this ultra-cold outflow,out to $\gtrsim120,000$ AU. We find that in the ultra-cold outflow, themass-loss rate (dM/dt) increases with radius, similar to its expansion velocity($V$) - taking $V\propto r$, we find $dM/dt \propto r^{0.9-2.2}$. The mass inthe ultra-cold outflow is $\gtrsim3.3$ Msun, and the Boomerang's main-sequenceprogenitor mass is $\gtrsim4$ Msun. Our high angular resolution ($\sim$0".3) COJ=3-2 map shows the inner bipolar nebula's precise, highly-collimated shape,and a dense central waist of size (FWHM) $\sim$1740 AU$\times275$ AU. Themolecular gas and the dust as seen in scattered light via optical HST imagingshow a detailed correspondence. The waist shows a compact core in thermal dustemission at 0.87-3.3 mm, which harbors $(4-7)\times10^{-4}$ Msun~of very large($\sim$mm-to-cm sized), cold ($\sim20-30$ K) grains. The central waist(assuming its outer regions to be expanding) and fast bipolar outflow haveexpansion ages of $\lesssim1925$ yr and $\le1050$ yr: the "jet-lag" (i.e.,torus age minus the fast-outflow age) in the Boomerang supports models in whichthe primary star interacts directly with a binary companion. We argue that thisinteraction resulted in a common-envelope configuration while the Boomerang'sprimary was an RGB or early-AGB star, with the companion finally merging intothe primary's core, and ejecting the primary's envelope that now forms theultra-cold outflow.

The Coldest Place in the Universe: Probing the Ultra-Cold Outflow and Dusty Disk in the Boomerang Nebula