November 6, 2008

Astronomers Closer To Solving Dark Matter Riddle

Scientists believe they may now have a better idea of where to search for dark matter thanks to the results of a giant computer simulation reported on Wednesday.

Dark matter has puzzled scientists for about 75 years when they discovered its existence from its gravitational effects. The mysterious matter is considered to account for 85 percent of the universe's mass although it cannot be seen through telescopes.

Researchers at the international Virgo Consortium, including cosmologists at Durham University, reported their new findings in the journal Nature.

"Discovering what dark matter is, is one of the most fundamental questions scientists can ask," said Carlos Frenk, a cosmologist at Durham University in Britain.

Using a massive computer simulation of the evolution of a galaxy like the Milky Way, scientists were able to "see" gamma-rays given off by dark matter.

Their findings could help NASA's Fermi Telescope in its search for the dark matter and open a new chapter in our understanding of the Universe.

"Uncovering the identity of the main component of the universe. That is what this is about," said Frenk.

Dark matter does not reflect nor normally shine, but astronomers can "see" its effects by observing how its gravity bends light given off by more faraway galaxies.

The Virgo Consortium looked at dark matter halos "“ structures surrounding galaxies "“ which contain a trillion times the mass of the Sun.

Their simulations "“ called The Aquarius Project - showed how the galaxy's halo grew through a series of violent collisions and mergers between much smaller clumps of dark matter that emerged from the Big Bang.

The researchers found that gamma-rays produced when particles collided in areas of high dark matter density could be most easily detectable in regions of the Milky Way lying close to the Sun in the general direction of the galaxy's centre.

They suggest the Fermi Telescope should search in this part of the galaxy where they predict that gamma-rays from dark matter should glow in "a smoothly varying and characteristic pattern".

Frenk said that these new clues may allow astronomers to finally solve the "dark matter riddle."

"The search for dark matter has dominated cosmology for many decades. It may soon come to an end."


Image Caption: This photo from NASA of the Bullet Cluster indicates what is believed to be dark matter (represented in blue) in the photo. Source: NASA / CXC / CIA / STSci / Magellan / Univ. of Ariz. / ESO.


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