Mitchell Institute for Fundamental Physics & Astronomy
College Station, Texas 77843
With its most recent data releases, European Space Agency’s Gaia mission revealed the fossilised record of a dramatic - and long suspected - accretion event in the distant past of our Galaxy. This head-on collision with a massive dwarf galaxy was a turning point in the evolution of the Milky Way and unleashed a series of transformations that forever changed the Galaxy. This unprecedented metamorphosis is the focus of this talk. I will discuss the time, the geometry and the kinematics of the interaction, and elucidate the response of the Milky Way to the massive intruder.