Our cannibalistic neighbor, Andromeda, has set its sights on the Milky Way.
Andromeda has eaten several smaller galaxies within the last few billion years.
There are traces of more small galaxies that Andromeda gobbled up even earlier, perhaps as far back as 10 billion years when it was first forming.
The Milky Way is on a collision course with Andromeda in about four billion years.
The direction of the ancient feeding is the same as the alignment of dwarf galaxies orbiting Andromeda.
The study, published in Nature, analysed data from the Pan-Andromeda Archaeological Survey, known as PAndAS.
"We are cosmic archaeologists, except we are digging through the fossils of long-dead galaxies rather than human history," said Professor Lewis, who is a leading member of the survey.
Australian National University