• Elementary Particles In 1928, Paul Dirac developed an equation for combining quantum theory and special relativity. The solution contained an electron with positive energy, and a positive electron (positron) with negative energy.  For over fifty years, physicists have been building accelerators to discover new elementary particles (six quarks, six leptons, six anti-quarks and six anti-leptons) along with their force carriers. Scientists have confirmed matter-antimatter symmetry between the elementary particles.

• Plasma Cosmology  In 1966, Hannes Alfven developed the Plasma Universe Model.  In the center of galaxies, there are two black holes.  The black holes are ejecting matter and antimatter in opposite directions into space to form spiral arms of matter and antimatter stars.  Anthony Peratt has developed computer models that simulated the known galaxies in the universe.  In our galaxy, the sun is one of the billions of stars that are composed of matter. There are a similar number of antimatter stars. 
• Comets  In 2002, Norm Hansen announced the discovery that comets are composed of antimatter to joint meeting of American Physical Society and American Astronomical Society. The comet's plasma coma and tails are created by the solar wind and dust particles blasting antimatter fragments, dust and ions off the comet's surface.  Light and x-rays, which we see, is produced from matter-antimatter annihilation taking place on the comet's surface and in the plasma coma and tails. Sungrazer comets produce enormous explosions and solar flares when they collided with the sun.

Within the Milky Way Galaxy, matter-antimatter symmetry exists from the matter/antimatter black holes, stars/anti-stars, planets/anti-planets, asteroids/comets, solar/comet dust particles, solar wind/comet ions, elements/anti-elements, quarks/anti-quarks and leptons/anti-leptons.