Milky Way ‘Ate’ a Nearby Dwarf Galaxy 10 Billion Years Ago, Study FindsHubble Captures Mature ‘Pinwheel’ Galaxy in Stunning Image Stay on target A new discovery by researchers at the University of Michigan helped uncover the Milky Way’s long-lost (and long extinct) sibling.Richard D’Souza and Eric Bell, of the UM Department of Astronomy, have uncovered the sordid history of our closest large galactic neighbor, the Andromeda galaxy.As the story goes, Andromeda cannibalized a massive galaxy two billion years ago.Though mostly shredded, the nebula left behind “a rich trail of evidence,” helping scientists understand how disk galaxies like the Milky Way evolve and survive.“Astronomers have been studying the Local Group [of galaxies]—the Milky Way, Andromeda, and their companions—for so long,” according to Bell. “It was shocking to realize that the Milky Way had a large sibling, and we never knew about it.”It turns out the disrupted galaxy, named M32p, would have been massive—at least 20 times larger than any that merged with the Milky Way—making it the third-largest member of the so-called Local Group.Its dismantling billions of years ago resulted in a nearly invisible halo of stars, and the creation of Andromeda’s enigmatic M32 satellite galaxy.“M32 is a weirdo,” Bell said. “While it looks like a compact example of an old, elliptical galaxy, it actually has lots of young stars. It’s one of the most compact galaxies in the universe. There isn’t another galaxy like it.”Using new computer simulations, D’Souza and Bell were able to understand that most of the stars in Andromeda’s faint outer halo were created by the shredding of a large nebula.“It was a ‘eureka’ moment,” D’Souza said. “We realized we could use this information … to infer the properties of the largest of these shredded galaxies.”Their findings, published in the journal Nature Astronomy, mark a breakthrough in the study of stars and other planets.The understanding that Andromeda’s disk survived an impact with a massive galaxy calls into question traditional understanding these sorts of interactions would destroy disks and form an elliptical galaxy.“The Andromeda Galaxy, with a spectacular burst of star formation, would have looked so different two billion years ago,” Bell explained. “When I was at graduate school, I was told that understanding how the Andromeda Galaxy and its satellite galaxy M32 formed would go a long way toward unraveling the mysteries of galaxy formation.”The computer models used in this study can be applied to other galaxies, as well.Let us know what you like about Geek by taking our survey.