https://www.theregister.co.uk/2018/07/06/suasage_galaxy_collision/

Around eight to ten billion years ago, a neighbouring dwarf galaxy known as the Sausage galaxy smashed into the Milky Way leaving a smattering of gas, dust, and stars.

A team of astrophysicists have traced back the leftover debris to piece together the cosmic catastrophe detailed in a paper published in the Monthly Notices of the Royal Astronomical Society.