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Studying galactic interactions is like sifting through the forensic evidence at a crime scene. Astronomers wade through the debris of a violent encounter, collecting clues so they can reconstruct the celestial crime to determine when it happened. Take the case of M82, a small, nearby galaxy that long ago bumped into its larger neighbor, M81. When did this violent encounter occur? New infrared and visible-light pictures from NASA's Hubble Space Telescope reveal for the first time important details of large clusters of stars, which arose from the interaction. Hubble's sharp eye spied more than ...