 This simulation shows a Milky Way-like galaxy around five billion years ago when most satellite galaxy collisions were happening. Credit: Andrew Cooper/John Helly, Durham University |
Many of the Milky Way's ancient stars are remnants of other smaller galaxies torn apart by violent galactic collisions around five billion years ago, according to researchers at Durham University.
Scientists at Durham's Institute for Computational Cosmology and their collaborators at the Max Planck Institute for Astrophysics, in Germany, and Groningen University, in Holland, ran huge computer simulations to recreate the beginnings of our galaxy.
The simulations revealed that the ancient stars, found in a stellar halo of debris surrounding the Milky Way, had been ripped from smaller galaxies by the gravity generated by colliding galaxies.
Cosmologists predict that the early Universe was full of small galaxies which led short and violent lives. These galaxies collided with each other leaving behind debris which eventually settled into more familiar looking galaxies like the Milky Way.
The researchers say their finding supports the theory that many of the Milky Way's ancient stars had once belonged to other galaxies instead of being the earliest stars born inside the galaxy when it began to form about 10 billion years ago.
The research, funded in the UK by the STFC, appears in the Monthly Notices of the Royal Astronomical Society.
Lead author Andrew Cooper, from Durham University's Institute for Computational Cosmology, said: "Effectively we became galactic archaeologists, hunting out the likely sites where ancient stars could be scattered around the galaxy.
"Our simulations show how different relics in the galaxy today, like these ancient stars, are related to events in the distant past.
"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."
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