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Galactic positronium mystery deepens.

Galactic positronium mystery deepens

Observations over the last decade have shown that somewhere toward the center of the galaxy is an object containing a large amount of positronium, which is made up of electrons and their antiparticles positrons bound together. Gradual annihilation of the positronium yields gamma rays with a characteristic energy of 511 kilo-electron-volts. So much antimatter in our part of the universe is very unusual. Now observations with the HEAO 3 satellite and subsequent balloon flights show that the brightness of this object varies over time, reports Alan S. Jacobson of Caltech's Jet Propulsion Laboratory, thus deepening its mystery. However, the variations allow a limit to be set to its size--10.sup.13 kilometers. It could be a cloud surrounding a black hole that is a good source of positrons.
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Title Annotation:new observations of antimatter in center or galaxy
Author:Thomsen, Dietrick E.
Publication:Science News
Date:Jul 19, 1986
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