Milky Way galaxy flipped upside down after mega crash, Sun's path may have changed

The Milky Way may have dramatically flipped upside down billions of years ago after a violent collision with another galaxy, according to new research that sheds light on one of the biggest mysteries surrounding our home galaxy.Astronomers from Durham University have found evidence suggesting that the Milky Way's flat spiral disc changed its orientation by more than 90 degrees following a massive head-on collision around 10 to 11 billion years ago. The findings were presented at the Royal Astronomical Society's National Astronomy Meeting in Birmingham.The discovery could explain why the Milky Way's vast stellar halo, a sparse cloud of ancient stars surrounding the galaxy, rotates unusually slowly, something that has puzzled astronomers since observations from the European Space Agency's Gaia mission revealed the phenomenon. Halo 18 is an example of a galaxy that had a head-on collision and had a disc flip.