it was natural to examine whether any other stable isotopes of hydrogen, and particularly 3 H (triterium, symbol T), are present in ordinary hydrogen. In this article an account will be given of ...

This isotope is found at a ratio of about one per 2,500 helium-4 ions, the latter being the common version of helium. The sun just released a burst of a rare form of helium known as helium-3 (3 He).