* Astronomy

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RE: Antimatter

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Astronomers search for antimatter in colliding galaxies

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RE: Antimatter

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Underground Lab Probes How Matter Licked Antimatter
Everything in our universe is made of matter, but a century of physics has revealed that at the beginning of time, an exactly equal amount of antimatter existed. Then, two seconds after the Big Bang, something changed and suddenly there was more matter than antimatter. What we don't know is how matter won and opened the door to existence as we know it.
Now, in a former salt mine next door to a nuclear weapons waste repository, Stanford physicists are completing the installation of a new particle detector, the Enriched Xenon Observatory 200, that they hope will provide the answer to that question.

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Antimatters science fiction debut
Like everyone in his profession, John W. Campbell, Jr., editor of Astounding Science Fiction magazine, kept a watchful eye on new developments in nuclear physics, astronomy, and other sciences. Any scientific news might provide an idea for a science fiction story. Campbell kept in touch with dozens of authors, continually suggesting situations, backgrounds, and gimmicks. As an example, stories about uranium power started appearing in the pages of Astounding shortly after scientists discovered fission.

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The collision of entire clusters of galaxies has helped set the strongest limit yet on the amount of antimatter in the universe. 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 we can tell, 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.

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Title: When Clusters Collide: Constraints On Antimatter On The Largest Scales
Authors: Gary Steigman

Observations have ruled out the presence of significant amounts of antimatter in the Universe on scales ranging from the solar system, to the Galaxy, to groups and clusters of galaxies, and even to distances comparable to the scale of the present horizon. Except for the model-dependent constraints on the largest scales, the most significant upper limits to diffuse antimatter in the Universe are those on the Mpc scale of clusters of galaxies provided by the EGRET upper bounds to annihilation gamma-rays from galaxy clusters whose intra-cluster gas is revealed through its x-ray emission. On the scale of individual clusters of galaxies the upper bounds to the fraction of mixed matter and antimatter for the 55 clusters from a flux-limited x-ray survey range from < 5 x 10^(-9) to < 1 x 10^(-6), strongly suggesting that individual clusters of galaxies are made entirely of matter or, of antimatter. X-ray and gamma-ray observations of colliding clusters of galaxies, such as the Bullet Cluster, permit these constraints to be extended to even larger scales. If the observations of the Bullet Cluster, where the upper bound to the antimatter fraction is found to be < 3 x 10^-6, can be generalised to other colliding clusters of galaxies, cosmologically significant amounts of antimatter will be excluded on scales of order 20 Mpc (5 x 10^(15)M_Sun).

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Fire antimatter at matter and you would expect to see some spectacular fireworks. But not always, it seems. Sometimes, antimatter can bounce off matter, casting doubt on the long-held notion that a collision between matter and antimatter always makes for an explosive annihilation.
In 2004, Evandro Lodi Rizzini of Brescia University in Italy and colleagues reported the results of an experiment using a beam of antiprotons created by the Low Energy Antiproton Ring at CERN, near Geneva, Switzerland. They fired the antiprotons into a long aluminium cylinder filled with either hydrogen, deuterium or helium gas. The antiprotons, which had energies ranging from 1 to 10 kiloelectronvolts (keV), were duly annihilated in the gas. The team was able to explain the annihilation of nearly 70 per cent of the antiprotons, which had been slowed down and captured by an atom of gas.

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New experiments are being proposed to test a big unknown in physics: how antimatter reacts to gravity.
Physicists have studied antimatter, the mirror version of ordinary matter, for decades. They know, for example, that antiparticles have the same mass as ordinary particles, but opposite charge. But no one knows what effect gravity will have on such particles.
Now several groups want to measure exactly how the Earth will pull on antimatter. The tests would create a horizontal beam of the stuff and measure how much gravity deflects it.

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A new physics discovery explores why there is more matter than antimatter in the universe.
The latest research findings, which involved significant contributions from physicists at the University of Melbourne, have been recently published in the prestigious journal Nature.
The paper reveals that investigation into the process of B-meson decays has given insight into why there is more matter than antimatter in the universe.

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