The Milky Way may have grown up faster than astronomers suspected
Most of the galaxy’s disk was in place before a major collision 10 billion years ago
Much of the Milky Way’s characteristic disk (seen edge-on in this image from the Gaia spacecraft) was already in place 10 billion years ago, when an interloper galaxy called Gaia-Enceladus/Sausage collided with it.
DPAC/Gaia/ESA (CC BY-SA 3.0 IGO)