【#Tech24H】Researchers at Durham University, UK, carried out supercomputer simulations and concluded that the Milky Way likely suffered a "major flip" roughly 10 billion years ago amid a collision with a dwarf galaxy, tilting the whole galactic disk by over 90 degrees. Known as galactic disk flipping, this phenomenon accounts for the abnormally slow rotation of the Milky Way’s stellar halo and offers fresh evidence to trace the evolution of the Milky Way and its dark matter halo. In addition, the study confirms a strong correlation between the rotation of the stellar halo and the dark matter halo. It implies the two structures co-evolved while the Milky Way kept accreting tiny satellite galaxies. The finding charts new research paths for probing the Milky Way’s formation timeline and dark matter distribution, enabling scientists to better decipher the evolution of comparable galaxies.