Click for next articleAn artist's impression of the collision between the Milky Way and the Gaia-Sausage-Enceladus dwarf galaxy. The Milky Way's spiral disk may have flipped over by 90 degrees, in turn altering the solar system's orbit around the center of the galaxy. "So, we think that the Milky Way disk likely flipped in the past." This collision was the last major impact that our Milky Way galaxy experienced, but maybe not the last major event that it experienced. At some point, the Milky Way's disk seems to have also flipped, but what caused this is uncertain.