Ask astronomers about dark matter and one of the things they talk about is that this invisible, mysterious 'stuff' permeates the universe. In particular, it exists in halos surrounding most galaxies.
and one of the things they talk about is that this invisible, mysterious 'stuff' permeates the universe. In particular, it exists in halos surrounding most galaxies.The mass of the halo exerts a strong gravitational influence on the galaxy itself, as well as on others in the neighborhood. That's pretty much the standard view of dark matter and its influence on galaxies.
It contains a number of dwarf galaxies with distorted, perturbed shapes. This is odd, especially if they should be surrounded by dark matter halos.Let's take a quick look at dwarf galaxies. They're small and faint and usually found riding along in galaxy clusters or near much larger companions. The Milky Way Galaxy has a coterie of dwarf galaxies around it.
"This is because, according to that model, the dark matter halos of these dwarfs should partly shield them from tides raised by the cluster."Kroupa and Ph.D. student Elena Ascencio analyzed observations of the perturbed dwarfs in Fornax. They wanted to understand the extent of gravitational distortions these galaxies show and what causes them.
"The comparison showed that, if one wants to explain the observations in the standard model," she said,"the Fornax dwarfs should already be destroyed by gravity from the cluster center even when the tides it raises on a dwarf are sixty-four times weaker than the dwarf's own self-gravity."
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