This element was discovered by J. Berzelius in 1817 in Stockholm. Its name alludes to the moon, Selene in Greek.

Ionization energies
SeI 9.75 eV, SeII 21.2 eV, SeIII 30.8 eV.

No Se I or Se II lines have been observed in the sun.

Se in stars
Bidelman (1966) announced the probable detection of SeII in one Ap star of the Cr-Eu-Sr subgroup.

Se occurs in the form of six stable isotopes, Se 74, 76, 77, 78, 80 and 82, which occur in the solar system with frequencies 1%, 9%, 8%, 23%, 50% and 9% respectively. There also exist 14 short-lived isotopes and isomers, among them Se79 with a half life of 7 × 104 years.

Se74 can only be produced by the p process, Se76 by the s process and the p process. Se 77,78 and 80 are produced by the r process and the s process. Se82 is a pure r process product.

Published in "The Behavior of Chemical Elements in Stars", Carlos Jaschek and Mercedes Jaschek, 1995, Cambridge University Press.