PORTLAND, Ore. As much as 96 percent of the known Universe seems to be missing. Called dark matter or dark energy, the missing elements do not appear to emit or reflect enough electromagnetic radiation to be directly observed. Thus, they must be inferred from their gravitational effects on visible matter.
Some researchers have proposed quantum effects as an explanation of the location of missing dark energy, but other astrophysicists claim there should be much more dark matter concentrated in the center of distant galaxies.
Researchers at McMaster University (Hamilton, Ontario) now claim to have located the missing dark matter in a halo around galaxies. Using a supercomputer to create the most accurate model yet of galaxy formation, the researchers claim the missing matter was there all along, just not where researchers expected it to be.
The key to finding the missing matter was adding more detail to the models used to explain the violent formation of new galaxies, in particular the relationship between interstellar gas and dark matter. The current model dubbed, "cold dark matter cosmology," is correct, but needed a more detailed simulation, according to Sergey Mashchenko, a research associate in the Department of Physics & Astronomy at McMaster University. He said the problem is in the model's prediction that much more dark matter should be concentrated in the center of distant galaxies than is observed.
|Galaxy formation sloshes intersellar gases (where colors from violet to blue to green to white correspond to gases of increasing density) into halo around stars (yellow) in center.
(Photo courtesy of S. Mashchenko, J. Wadsley, and H. M. P. Couchman)|
According to Mashchenko, the cold dark matter model works on a large scale, but lacks the details necessary to predict the composition of individual galaxies. He claims his model provides the missing details about the violent birthing processes of new galaxies, which form from dense clouds of star dust, eventually growing so massive that they explode in a supernova.
These supernova, according to more detailed model, push vast interstellar gas clouds in a sloshing effect that forces the missing dark matter out to the edges of the galaxies. Thus the dark matter that was previously thought to be missing from the Universe is actually located in an invisible halo around them, according to this new more detailed model.
Mashchenko's supercomputer simulations were run on the Shared Hierarchical Academic Research Computing Network that includes a consortium of colleges and universities each of which contributes a cluster of high-performance computers, linked by fiber optics into a cluster of clusters.