Violent Collision May Have Destroyed Milky Way’s First Stellar Disk

New simulations suggest a violent collision 11 billion years ago reshaped our Galaxy and triggered a burst of star formation. This image from the Gemini North telescope shows a pair of interacting spiral galaxies: NGC 4568 (bottom) and NGC 4567 (top).

Violent Collision May Have Destroyed Milky Way’s First Stellar Disk. New simulations suggest a violent collision 11 billion years ago reshaped our Galaxy and triggered a burst of star formation. This image from the Gemini North telescope shows a pair of interacting spiral galaxies: NGC 4568 (bottom) and NGC 4567 (top). The Milky Way’s disk is a sprawling, rotating structure of stars and gas shaped somewhat like a cosmic pancake, with bright spiral arms extending outward from its center. Most of the Galaxy’s stars — including the Sun — reside within this disk, which spins through space at speeds exceeding 220 km per second. For decades, astronomers have been trying to pinpoint when this vast rotating structure first emerged. “A key clue lies in the motions and ages of the stars: at some point in the Galaxy’s early history, the stars began...