Many of the Milky Way's ancient stars derive from other smaller galaxies torn apart by violent galactic collisions, say researchers at Durham University.
Computer simulations show that the stars, found in a halo of debris surrounding the Milky Way, were ripped away by the gravity generated by colliding galaxies five billion years ago.
"Our simulations show how different relics in the galaxy today, like these ancient stars, are related to events in the distant past," says lead author Andrew Cooper.
"Like ancient rock strata that reveal the history of Earth, the stellar halo preserves a record of a dramatic primeval period in the life of the Milky Way which ended long before the Sun was born."
The computer simulations started from the Big Bang, around 13 billion years ago, and used the universal laws of physics to simulate the evolution of dark matter and the stars.
These simulations are the most realistic yet, says the team, capable of zooming into the very fine detail of the stellar halo structure.
"The simulations are a blueprint for galaxy formation. They show that vital clues to the early, violent history of the Milky Way lie on our galactic doorstep," says Professor Carlos Frenk, director of Durham University's Institute for Computational Cosmology.
"Our data will help observers decode the trials and tribulations of our galaxy in a similar way to how archaeologists work out how ancient Romans lived from the artefacts they left behind."