In an article on New Scientist Space, Stephen Battersby tells us about NGC 4736, a spiral galaxy that lies 15 million light years away. It is a puzzling galaxy in that it seems to be missing it’s missing mass (dark matter).
Current theory predicts that galaxies form within dark matter halos, enormous clumps of dark matter. In most galaxies, as you look farther out from the galactic core, the stars are moving faster than can be accounted for with the luminous ‘normal’ matter. Hence the prediction of dark matter, the invisible stuff that keeps galaxies spinning like overclocked tops.
Joanna Jalocha, Lukasz Bratek and Marek Kutschera of the Polish Academy of Science in Krakow used a model that combines the rotation curve of the galaxy with measurements of the density of hydrogen gas. Their model predicts that the motion of NGC 4736 can be accounted for with normal matter.
So, is something wrong with the the model, or is something wrong with the theory?
It appears far more likely that these predictions are incorrect, that the model is built on incomplete data. So the missing missing mass might really be not missing after all… or something.