For a few years now, most cosmologists have been pretty happy with the idea of dark matter – a kind of invisible, as yet undetectable matter that seems nevertheless to make a huge proportion of the actual matter in the universe.
Rather than observing it directly, astronomers have viewed its effects, thus inferring where the invisible stuff actually lies. And there they've run into a problem. A leading model for the stuff, called Cold Dark Matter cosmology, has seemed to suggest that there should be much more dark matter at the center of galaxies than observations actually show.
However, researchers using a supercomputer simulation of the early formation of a dwarf galaxy now argue that this may not be such a problem after all.
In their simulation, they modeled the effects of early, violent interactions between gas clouds and dark matter. Much of the dense gas forms massive stars, which collapse and turn into supernovas – and this process winds up explaining what we actually see in the universe.
"These huge explosions push the interstellar gas clouds back and forth in the center of the galaxy," said McMAster University research associate Sergey Mashchenko, the lead author of the study, in a statement. "Our high-resolution model did extremely accurate simulations, showing that this 'sloshing' effect -- similar to water in a bathtub -- kicks most of the dark matter out of the center of the galaxy."
The simulations were carried out using the Shared Hierarchical Academic
Research Computing Network. Mashchenko's paper was published in the
Nov. 29 issue of Science.
Scientists solve cosmological puzzle [McMaster University press release]
(Image: A dwarf galaxy forming. Inset is the central 2000 light years of the galaxy, where star motions force movement in the gas. Credit: S.
Mashchenko, J. Wadsley, and H. M. P. Couchman)
