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.
The dark matter map was created with observations from the Hubble telescope of a large galaxy cluster called Abell 1689, located 2.2 billion light-years from Earth. This cluster is famous as a stunning example of gravitational lensing – a phenomenon predicted by Einstein that happens when massive objects warp the space-time around them, causing even light to travel on a bent path when it passes by.
When astronomers look at Abell 1689, they can see distorted pictures of the galaxies that lie beyond it in our line of sight: As those galaxies' light travels from them to us, it passes through Abell 1689 and is bent and magnified.
By studying this so-called lensing effect, scientists can deduce the mass that is causing the warping.
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 lensed images are like a big puzzle," Coe said. "Here we have figured out, for the first time, a way to arrange the mass of Abell 1689 such that it lenses all of these background galaxies to their observed positions."
Above: the new map of dark matter12 November 2010
01:29 pm ET
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