An upper limit of 60 GeV is derived on the mass of a stable heavy neutrino, using the standard big bang model. This is in addition to the previous limits which constrain the mass of a neutrino to be less than 50 eV or greater than 10 GeV. Thus, we predict that in the near future all existing types of stable neutrinos will be detected.
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This work has been stimulated by the Summer School on Physical Cosmology at Les Houches We would hke to thank J Audouze and R Kochhar for their assistance in preparing this paper We would also hke to thank D N Schramm, P J E Peebles and G A Tammann for valuable discussions This work has been supported in part by the Fanme and John Hertz Foundation and NSF grant AST 78-21402 at the University of Ctucago