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Quoted By:
http://space.newscientist.com/article/dn13280-galaxy-without-dark-matter-puzzles-astronomers.html
Great puzzle
McGaugh points out that other galaxies have shown declining rotation curves, but later observations have always shown that beyond a certain distance, they flatten out, which can't be explained by ordinary gravity from visible stars and gas. "If we believe this decline, it seems like the exception and not the rule," he says.
Even then, one exceptional dark-matter-less galaxy would be a great puzzle. "The current picture is that galaxies form inside of dark matter halos," Diemand told New Scientist. The dark matter's gravity attracts ordinary gas, which can then coagulate into stars.
"It is unclear how one would form a galaxy without a dark halo, or how one could remove the halo without destroying the galaxy," says Diemand. "A galaxy without dark matter really does not fit into our current understanding of cosmology and galaxy formation."
Nor can galaxies with declining rotation curves be easily explained by MOND, says McGaugh. So for now, it seems that some of our missing mass is missing.
Great puzzle
McGaugh points out that other galaxies have shown declining rotation curves, but later observations have always shown that beyond a certain distance, they flatten out, which can't be explained by ordinary gravity from visible stars and gas. "If we believe this decline, it seems like the exception and not the rule," he says.
Even then, one exceptional dark-matter-less galaxy would be a great puzzle. "The current picture is that galaxies form inside of dark matter halos," Diemand told New Scientist. The dark matter's gravity attracts ordinary gas, which can then coagulate into stars.
"It is unclear how one would form a galaxy without a dark halo, or how one could remove the halo without destroying the galaxy," says Diemand. "A galaxy without dark matter really does not fit into our current understanding of cosmology and galaxy formation."
Nor can galaxies with declining rotation curves be easily explained by MOND, says McGaugh. So for now, it seems that some of our missing mass is missing.
