Galactic superclash proves rarity of antimatter in the Universe

September 3rd, 2008 - 3:44 pm ICT by ANI  

London, September 3 (ANI): A research on the collision of entire clusters of galaxies has helped set the strongest limit yet on the amount of antimatter in the Universe, proving that it exists in rarity.

According to a report in New Scientist, the research suggests that if antimatter exists in large amounts, it may have been pushed to the far reaches of the universe in the moments after the big bang.

In the early universe, the theory goes, matter and antimatter, which has the same mass as matter, but the opposite charge, should have been created in equal amounts.

But as far as scientists have estimated, our universe is made of matter.

In our galaxy, for instance, no primordial anti-protons or anti-helium atoms have been found by satellite or balloon-based experiments.

Its 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, US.

Recently, astronomers have looked for signs of antimatter on an even larger scale galaxy clusters, which each typically contain hundreds of galaxies.

If any fraction of a clusters gas is a mixture of matter and antimatter, then the two types of matter should annihilate on contact, producing gamma rays instead of the X-rays expected from collisions between matter particles.

Now, Steigman has studied X-rays and gamma rays from two galaxy clusters that collided, producing the Bullet Cluster, which was discovered in 2006.

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.

The research has implications for the theory of inflation, a period in which space expanded exponentially moments after the big bang.

Inflation could have separated neighbouring regions of matter and antimatter before they annihilated each other.

Figuring out if there is any antimatter within the observable universe could tell cosmologists about how long inflation lasted.

For instance, 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.

According to Steigman, Thats why there is interest in whether we have entirely excluded antimatter (from the universe) or simply forced it to a very large scale. (ANI)

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