annihilation radiation

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an·ni·hi·la·tion ra·di·a·tion

the radiation resulting when a positron from beta-positive decay comes to rest. It encounters an electron, and the two particles annihilate each other and convert their rest mass into two 0.51-MeV gamma rays emitted in exactly opposite directions. See: pair production.
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References in periodicals archive ?
A year-long study with a GRO detector has for the first time mapped in detail the distribution of this emission along the plane of the galaxy To the astonishment of astronomers, it also recorded a broad distribution of the same annihilation radiation in a region some 3,000 light-years out from the disk of the Milky Way.
Although the source of the annihilation radiation is debatable, there is no dearth of candidates in the crowded environs of the galactic center.
Matter falling onto such a compact object would produce low-energy gamma rays, which in turn would generate the positrons needed to produce the annihilation radiation.