Computer simulation of the merger between a galaxy like the young Milky Way, whose stars are shown in cyan, and a smaller galaxy, indicated in red.
According to a study based on the second data release of ESA’s Gaia mission, astronomers estimate that a significant merging event like the one shown in this animation has occurred during the Milky Way’s early formation stages, ten billion years ago. Such a merger has led to two important components of our Galaxy, the halo and the thick disc.
Stars belonging to the accreted galaxy, which has been named Gaia-Enceladus, are interspersed with the Milky Way stars and can be seen across the entire sky, but could only be revealed thanks to Gaia’s extraordinary precision.
Credit: Koppelman, Villalobos & Helmi, Kapteyn Astronomical Institute, University of Groningen, The Netherlands