Gaia detects a shake in the Milky Way. Position and movement data of more than 6M stars show substructures that were never seen, originated by an impact that occurred more than 300 million years ago

See the source article by following the link below:
Gaia detects a shake in the Milky Way. Position and movement data of more than 6M stars show substructures that were never seen, originated by an impact that occurred more than 300 million years ago