OUR galaxy may still be reeling from a massive collision with another galaxy 2 billion years ago.
Some groups of stars near our solar system move with unusually high velocities compared with others in the galactic disc. Ivan Minchev of the University of Strasbourg, France, says their pattern and velocity can be explained if they were thrown by the shock of a past smash.
Minchev developed a computer simulation of the distribution of velocities of billions of stars. This is far more than have been modelled previously, says co-author Alice Quillen of the University of Rochester in New York.
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A pattern of 鈥渞ipples鈥� emerged in Minchev鈥檚 enormous starscape, with bands of stars travelling at the same high velocity. He suggests these stars were jolted by a shock wave from another galaxy merging with ours 鈥� an event that other observations already point to. This smash caused pulsations of energy in the galactic disc akin to waves in a pond, says Minchev.
The model fits closest with actual measurements if the collision happened about 2 billion years ago. The work has been submitted to Monthly Notices of the Royal Astronomical Society ().
Minchev鈥檚 model contributes to a key debate in astronomy about the origin of these streams of fast-moving stars, says of the Free University of Brussels in Belgium.
