- A computer model shows how some of the Milky Way's ancient stars came from other galaxies.
- The simulation meshes with observational evidence of stellar transplants.
- Follow-on studies will fold stellar chemical evolution into the mix.
Stars are shown from a simulated Milky Way-like galaxy around five billion years ago, when most satellite galaxy collisions were happening. Click to enlarge this image.
Andrew Cooper, John Helly (Durham University)
Some of the oldest stars in the Milky Way are immigrants from other galaxies, survivors of cataclysmic collisions that tore apart smaller systems about 5 billion years ago.
Scientists developed a sophisticated new computer simulation that recreated the Milky Way's origin and evolution stemming back as far as time began, at least in our universe, with the Big Bang explosion roughly 13 billion years ago.
The model reveals new details about the halo of debris around the Milky Way and the clumps of stars and other matter it contains.
The simulation shows that a small percentage of the oldest stars in the halo hail from other galaxies, propelled by gravitational forces into streams that feed the Milky Way.
The research buttresses observational evidence showing that some stars in the galaxy predate the formation of the galaxy itself.
"This is a really great tool for understanding the earliest conditions of our galaxies," said Robert Massey with the Royal Astronomical Society in London.
One key to the simulation's accuracy is its portrayal of recently discovered gravitationally bound clouds of dark matter, formed outside the Milky Way, that have been incorporated, intact, into our galaxy. The computer model predicts these transplants, as well as a number of small galaxies that didn't survive their encounters with the Milky Way quite so smoothly.
The model is supported by observational evidence showing, for example, how a small elliptical galaxy known as Sagittarius is in the process of being shredded by the Milky Way.
"It's the smoking gun," lead researcher Andrew Cooper, with Durham University's Institute for Computational Cosmology, told Discovery News.
Researchers plan to continue to refine the program to incorporate results of ongoing chemical analysis of some of some of the galaxy's oldest stars.
The simulation also can jump ahead in time, showing how neighbor galaxies, such as the Large and Small Magellanic Clouds, will crash into the Milky Way one day, as well as how the Milky Way itself, will, in another two billion years or so, smash into Andromeda.
The research is published in the Monthly Notices of the Royal Astronomical Society.
Tags: Big Bang, Computer Simulation, Cosmology, Galaxies, Universe
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