Illustration of Positronium

1932-1951 Positronium

The book of science

Tom Sharp

Carl David Anderson, Stjepan Mohorovičić, Martin Deutsch particle physics Illustration of Positronium


Lighter than hydrogen, positronium is an onium of an electron bound to its antiparticle a positron orbiting their common center. One positronium is a single exotic atom; two or more of them make positronia. A positronium is metastable, meaning it doesn’t decay right away, but when it does (in about an eighth of a nanosecond), particle and antiparticle annihilate each other releasing gamma rays or photons.

Other oniums

True muonium Pionium Protonium Quarkonium


The Marx Brothers’ Duck Soup is set in the fictional country of Freedonia, diminutive, obscure, and autocratic. Generally, the names of particle-antiparticle exotic atoms end in “onium,” plural “onia.” The Duck Soup setting is only a coincidence.

The study of onia (oniumology?) has helped refine quantum field theory, quantum electrodynamics, quantum chromodynamics, and the theory of strong interactions among fundamental particles.

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