An Etymological Dictionary of Astronomy and Astrophysics

Unstable heavy → isotope of → hydrogen whose nucleus contains one → proton and two → neutrons. Tritium occurs naturally due to → cosmic rays interacting with atmospheric gases. In the most important reaction for natural tritium production, a fast neutron interacts with atmospheric nitrogen: ¹⁴N + n → ¹²C + ³T. Its → half-life is about 12 years. Tritium was formed in an intermediate step in light element synthesis in → early Universe.

See also: N.L., from Gk. trit(os) “third” (from → tri-

• -tos adj. suffix) + N.L. → -ium.