A big bang would produce only hydrogen, helium, and lithium, so the first generation of stars to somehow form after a big bang should consist only of those elements. Some of these stars should still exist, but despite extensive searches, none has been found (n).
n. “One might expect Population III stars [stars with only hydrogen and helium and no heavier elements] to have the same sort of distribution of masses as stars forming today, in which case some should be small enough (smaller than 0.8 the mass of the Sun) still to be burning their nuclear fuel. The problem is that, despite ex
tensive searches, nobody has ever found a zero-metallicity star.” Bernard Carr, “Where Is Population III?” Nature, Vol. 326, 30 April 1987, p. 829.
“Are there any stars older than Population II [i.e., Population III stars]? There should be, if our ideas about the early history of the universe [i.e., the big bang theory] are correct....There is no statistically significant evidence for Population III objects [stars].” Leif J. Robinson, “Where Is Population III?” Sky and Telescope, July 1982, p. 20.
“Astronomers have never seen a pure Population III star, despite years of combing our Milky Way galaxy.” Robert Irion, “The Quest for Population III,” Science, Vol. 295, 4 January 2002, p. 66.
Supposedly, Population II stars, stars having slight amounts of some heavy elements, evolved after Population III stars. Predicted characteristics of Population II stars have never been observed.
“Spectral studies of ancient [Population II] stars in the Milky Way haven’t turned up anything so distinctive [as the chemical elements that should be present], [Timothy] Beers notes, but the search continues.” Ibid., p. 67.