DARK matter has a dark secret: it has had long-term dealings with visible matter.
Theory predicts that the proportion of visible to dark matter should increase with time, so Fran莽ois Hammer, an astronomer at the Paris Observatory in France, and his colleagues used the Very Large Telescope at Cerro Paranal in Chile to examine 32 young galaxies 6 billion light years away. They compared the mass ratio of visible and dark matter in these galaxies with the ratio in galaxies that are close by 鈥� and therefore older. Surprisingly, the ratio was about the same in both young and old galaxies: one part visible matter to 30 parts dark. This hints at a previously unknown interaction between dark and visible matter, Hammer says.
The team also found that the motion of stars within about 40 per cent of the galaxies was more turbulent that it should be, suggesting that collisions played a more important part in the evolution of galaxies than our current understanding can explain. The results will appear in a forthcoming issue of Astronomy and Astrophysics.
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