Though invisible, dark matter makes its presence known through its gravitational tug on normal stuff. Scientists now calculate that dark matter could make up 80 percent of all the matter in the universe.
The new dark matter map could reveal secrets not just about dark matter, but about its equally enigmatic sibling, dark energy. This is the name given to the perplexing force that is pulling against gravity, causing the universe to balloon in size ever more rapidly. [New map of dark matter]
Astronomer Dan Coe of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and Edward Fuselier of the United States Military Academy at West Point teamed up to apply a new mathematical formulation to Hubble observations of Abell 1689. The result is the most accurate, detailed calculation so far of the cluster's mass distribution, including the mass that can't be accounted for by the visible matter – meaning, the dark matter.The new dark matter map reveals that Abell 1689 is denser at its center than physical models would predict.Hints of similar heavy centers have been found in other large galaxy clusters recently, he added.
Because the universe has been continually expanding since its birth, it was once much denser than it is now. The extra heavy cores of galaxy clusters suggest they were born during these early stages when such dense conglomerations of matter were around.
But if galaxy clusters did get an early start in forming, that presents a quandary, because scientists would expect to see a lot more of them around today.
That indicates that perhaps the force of dark energy was stronger in the young universe than scientists have thought. Because dark energy works against gravity, pulling matter apart, its force would have suppressed the formation of galaxy clusters, and could have counteracted the head start clusters had in forming, scientists think.
If the dense centers found in Abell 1689 and other large clusters hold for the larger sample, it will lend support to the idea that dark energy was stronger earlier in the universe. If not, then it could mean that these few mega clusters just happen to have been special.
All in all, scientists may be getting closer to solving the riddles of dark matter and dark energy than ever before. For example, detectors on Earth and in space are currently searching for elusive signals from dark matter that could reveal the nature of this befuddling matter.
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