According to a new scientific study, it may be that dark matter, the elusive stuff that binds galaxies together, but that cannot be directly observed, does not exist at all. It's either that, or it has a very unusual set of properties, astrophysicists at the University of St Andrews, in the United Kingdom, say. Scientific observations show that dark matter does not simply keep galaxies spinning, as the theory goes. Additionally, galaxies were supposed to only interact with the stuff through gravity alone, and this doesn't seem to be the case,
NewScientist reports.
Established knowledge on dark matter has it that the stuff helped galaxies form at first, by keeping them together. It is widely believed among astronomers that each galaxy in the Universe is found at the core of a large, dark-matter concentration, a model that fits the substance's hypothetical properties. Gravity is supposed to be the only thing connecting galaxies and dark matter, but experts noticed that there was more to their interactions than this.
However, since the concept of dark matter emerged, there have been controversies about how it is distributed in the Universe and in galaxies. Its existence and action can only be inferred by the way galaxies and stars move, as the stuff does not emit any light, on any wavelength. Some astronomers believe that it must be distributed in the same concentrations throughout each galaxy, whereas others say that its concentrations should be larger in galactic cores, on account of gravity's effects.
In a recent study, the normal matter at the cores of 28 galaxies of various shapes and sizes was analyzed. The results threw astrophysicists off-guard – the investigation revealed that, in regions where dark-matter density had dropped to one-quarter of its central value, nearly 500 percent more of the stuff existed, in relation to normal matter. The results were unexpected, because the theory predicted that the ratio of dark matter to normal matter should depend on a galaxy's history, as in previous collisions and interactions with black holes and other such things.
“There is absolutely no rule in physics that explains these results,” University of St Andrews expert Hong Sheng Zhao, a co-author of the new study, says. Details of the finds appear in the latest issue of the renowned scientific journal Nature. “Although this clearly shows much more interplay between normal and dark matter than expected, it is too early to say exactly what this means,” University of Leicester expert Mark Wilkinson adds. He has not been part of the investigation, but has urged caution in interpreting the results.
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