Scientists find that the Milky Way may have had a close brush with another galaxy in the relatively recent past (cosmically speaking):
A new study published Wednesday in Nature has tracked the motion of more than six million stars in our galaxy using the European Space Agency’s Gaia spacecraft. The research reveals that the Milky Way nearly collided with another nearby galaxy — called the Sagittarius dwarf galaxy — sometime in the past 300 to 900 million years. This cosmic “fender bender” set millions of stars moving like ripples on a pond, the authors say. […]
The shape wasn’t the only thing that surprised them. Scientists knew that the Milky Way has seen many collisions over its 13.5 billion year history. But they thought that was ancient history.