Ancient Merger May Have Tilted the Milky Way by Over 90 Degrees
Durham University researchers using supercomputer simulations say the Milky Way was probably rotated by more than 90 degrees in a head-on collision with the Gaia Sausage dwarf galaxy about 10 billion years ago, a gradual 'disc flip' that unfolded over hundreds of millions of years and helps explain the slow rotation of halo stars observed by Gaia; future mergers like Sagittarius and the Large Magellanic Cloud are unlikely to cause as dramatic a reshaping.
