New simulations and observations indicate the Milky Way likely experienced a dramatic disc flip of more than 90 degrees, probably triggered by a head-on collision with Gaia Sausage about 10 to 11 billion years ago, which helps explain the unusually slow rotation of the halo. Researchers from Durham University and colleagues report the finding at the Royal Astronomical Society meeting, with multiple outlets detailing how this ancient galactic upheaval reshaped our galaxy.
