Antimatter galaxies

All the particles mentioned have their anti-particles (designated by a bar above the particle symbol), except the photon and the mesons, who are their own antiparticles. We may think about antimatter as consisting of antiprotons and antineutrons in an antinucleus surrounded by antielectrons (i.e. positrons). Superficially, there would be no way to distinguish such antimatter from our matter (sometimes called koino matter). It has been proposed that the universe is made up of matter and antimatter as a requirement of the principle of symmetry. In that case some galaxies, which perhaps can be observed, should be made up of antimatter. When such antimatter galaxies (or material expelled fi-om them) collide with koino matter galaxies, both types of matter are annihilated and tremendous amounts of energy released. 

As far as we can see into the Universe, we don t observe any primordial antimatter. Within the limits of our present observational horizon the Universe is seen to contain only matter and no antimatter. The presence of cosmic antimatter would lead to observable traces of annihilation however the measurements of the extragalactic 7 ray flux indicate an absence of annihilation radiation, and the microwave background spectrum lacks a corresponding distortion. These findings preclude the existence of a significant amount of antimatter within tens of Megaparsecs, which is the scale of super-clusters of galaxies. 

A major scientific experiment devoted to the search for antimatter originating from outside of our galaxy is presently being conducted by NASA. The experiment is a part of the project aiming at studies of matter, antimatter and dark matter in space. This project, coordinated by the Department of Energy (DOE), is a large collaboration of more than 30 universities, and will be conducted with the help of a state-of-the-art... 

The origin of X-rays, 7-ray bursts and radiowaves that pervade the Galaxy is as mysterious as the cosmic-ray sources. Evidence is mounting that in most cases these phenomena are linked to violent explosions, thought to include neutron-star quakes, quark nuggets, supernovae, matter-antimatter annihilation, clumping of quasars and colliding stars. Of all space radiations radio phenomena have been studied in most detail. 

This makes it possible for equal amounts of matter and antimatter to exist together in the universe and accounts for only matter being found in our galaxy."... 

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