Astronomers have found stars dating from a long-ago collision between the Milky Way and another galaxy. The crash helps to explain why the Milky Way looks the way it does.
s 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.”