September 4, 2008

Cosmologists Strive To Better Understand Levels Of Antimatter

Researchers have recently sought to find evidence of antimatter in the form of large clusters of hundreds of galaxies. 

Research suggests that if large amounts of antimatter exist, it may have been pushed far into the universe shortly after the big band occurred.

Antimatter has the same mass as matter but contains an opposite charge. Experts hypothesize that matter and antimatter should have been created in equal amounts.

However, scientists say that our universe is only made up of matter.

"It's clear to a very high level of precision that our galaxy is made of [what] we by convention call 'ordinary matter'," said Gary Steigman of Ohio State University in Columbus.

Steigman is studying the X-rays and gamma rays coming from the collision of two galaxy clusters.

Gamma rays and X-rays are produced by the collision of matter and antimatter.

The fraction of mixed matter observed is less than a few parts per million. Steigman says this excludes any significant amount of antimatter on scales up to about 65 million light years.

Steigman says his findings support the theory of inflation, in which space was expanded on a large scale shortly after the big bang. Inflation could have separated nearby regions of matter and antimatter before they destroyed each other.

If researchers can determine the level of antimatter present within the universe, they would have a better idea of how long inflation lasted.

Some models of inflation suggest that antimatter that was once adjacent to matter would now be outside the observable universe. Other models show that it might be separated on the scale of superclusters of galaxies.

"That's why there is interest in whether we have entirely excluded antimatter [from the universe] or simply forced it to a very large scale," says Steigman.

Diego Casadei, a particle physicist at CERN near Geneva, Switzerland said Steigman "goes in the direction of saying that we live in a big 'bubble' of matter."

Image Courtesy M Markevitch/D Clowe/NASA/STScI/CXC/CfA/Magellan/U Arizona/ESO WFI


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