Galaxy-forming collision recreated

The researchers conducted a computer simulation of how Andromeda has evolved over time, and the results suggest the two galaxies collided around 9 billion years ago and became permanently fused in the present Andromeda galaxy about 5.5 billion years ago, the BBC reported.

While astronomers can detect galaxies at the very edge of the universe, there is still much that is unknown about those in our immediate neighborhood, known as the Local Group of galaxies, team leader Francois Hammer of the Paris Observatory says.

Around 40 galaxies, of which the biggest are the Milky Way and Andromeda, make up the Local Group.

"Many astronomers, especially specialists in this field, thought that the Andromeda galaxy could be the result of a major merger," Hammer said.

"However, this has never been tested and especially dated" until now, he said.

In their computer modeling, the astronomers were able to reproduce most of the distinctive properties of the Andromeda galaxy including the large thin disk including its giant ring of gas and dust, the massive central bulge, the gigantic thick galactic "disc" and a giant stream of old stars.

The simulations, requiring massive computational power, were run on high-performance computers at the National Astronomical Observatory of China and at the Paris Observatory, the BBC said.

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