Column densities as viewed perpendicular to the orbital plane and at times after the merger. The merger causes an outflow of material, with the field of ejecta dropping to lower and lower densities and column densities as it expands. At late times in the simulation, while the ejecta continues streaming outward, the bound merger product in the center of the system gradually reaches larger column densities as more material falls back to its surface. This video relates to a paper that appeared in Jan. 25, 2013, issue of Science, published by AAAS. The paper, by N. Ivanova at the University of Alberta in Edmonton, AB, Canada, and colleagues was titled, "Identification of the Long-Sought Common-Envelope Events."