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When Milky Way Collided With a Dwarf Galaxy | Skeptic Society Magazine
As the Milky Way was growing, taking shape, and minding its own business around 10 billion years ago, it suffered a massive head-on collision with another, smaller galaxy. That cosmic cataclysm changed the Milky Way’s structure forever, shaping the thick spirals that spin out from the supermassive black hole at the galaxy’s core. Two new studies — one published earlier this month, another still under peer review — describe the evidence for this previously unnoticed event. “This is a big step forward,” said Elena D’Onghia, an astrophysicist at the University of Wisconsin who is unaffiliated with the new research. “It’s interesting because we can finally see what the history of the Milky Way is.” To uncover evidence of the collision so many eons later, astronomers have to work like galactic archaeologists, sifting through myriad sources of surviving information to piece together a story consistent with the available evidence. Both research teams relied on data from the European Space Agency’s Gaia space telescope, which has spent years gathering exceptionally rich biographies of millions of stars — …