Ancient collision with the Gaia Sausage dwarf galaxy 10 billion years ago may have flipped the Milky Way by more than 90
Astronomers have recently revealed that a significant collision between the Milky Way and a dwarf galaxy known as the Gaia Sausage, which occurred around 10 billion years ago, may have dramatically altered the orientation of our galaxy. Researchers from Durham University presented their findings at the Royal Astronomical Society's National Astronomy Meeting, suggesting that this ancient impact could have flipped the Milky Way by over 90 degrees, reshaping its structure long before the formation of our solar system. The collision involved the Gaia Sausage slamming directly into the Milky Way, resulting in the dwarf galaxy being torn apart and its stars absorbed. This powerful impact likely initiated a gradual process known as a "disc flip," which reoriented the Milky Way's disc over hundreds of millions of years. Lead researcher Kirill Batrakov emphasized that this transformation was not instantaneous, taking a considerable amount of time to unfold. The study also aimed to explain the peculiar movements of stars in the Milky Way's halo, which orbit at significantly slower speeds compared to those in the galaxy's disc. The simulations indicated that this slow rotation is a remnant of the major collision, providing insight into the Milky Way's complex history. As the Milky Way continues to merge with smaller galaxies today, such as the Sagittarius dwarf galaxy, future collisions are expected to be less impactful due to the galaxy's increased mass since the Gaia Sausage event.
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