http://www.physorg.com/news/2011-10-dar ... epens.html
La matière noire bien réelle en astronomie devient de plus en plus mystérieuse, car les galaxies naines sont constituées à 99% de matière noire invisible et de 1% du type étoiles bien visibles !!!
Et cette matière noire n'est pas concentré au centre de la galaxie comme celle 1% visible, mais uniforme.
Et on ne sait strictement rien sur la nature de cette matière noire invisible qui agit sur la matière visible que par la gravitation.
Et cette matière noire inconnue représente la plus grande partie de la masse de l'univers !!
Dark matter mystery deepens
Dwarf galaxies are composed of up to 99 percent dark matter and only one percent normal matter like stars. This disparity makes dwarf galaxies ideal targets for astronomers seeking to understand dark matter.
Walker and his co-author Jorge Peñarrubia (University of Cambridge, UK) analyzed the dark matter distribution in two Milky Way neighbors: the Fornax and Sculptor dwarf galaxies. These galaxies hold one million to 10 million stars, compared to about 400 billion in our galaxy. The team measured the locations, speeds and basic chemical compositions of 1500 to 2500 stars.
"Stars in a dwarf galaxy swarm like bees in a beehive instead of moving in nice, circular orbits like a spiral galaxy," explained Peñarrubia. "That makes it much more challenging to determine the distribution of dark matter."
Their data showed that in both cases, the dark matter is distributed uniformly over a relatively large region, several hundred light-years across. This contradicts the prediction that the density of dark matter should increase sharply toward the centers of these galaxies.
"If a dwarf galaxy were a peach, the standard cosmological model says we should find a dark matter 'pit' at the center. Instead, the first two dwarf galaxies we studied are like pitless peaches," said Peñarrubia.
http://arxiv.org/PS_cache/arxiv/pdf/110 ... 2404v3.pdf