It is shown that neutrinos (massless or massive), produced with kinetic energies below ∼50 eV in a supernova, have bound orbits in the remnant neutron star. The binding is mediated by a radial weak-interaction force, caused by a gradient in the collective weak potential of the neutrons in the star. This force is also able to create spontaneously neutrino-antineutrino pairs. If the bound-neutrino sphere is not fully degenerate at low momenta, a cold neutron star will shine continuously antineutrinos with energies ≲50 eV, as a result of the density gradient in it. In principle, these effects can also be realized at smaller (e.g., solid) densities for sufficiently low neutrino energies.

• Received 21 August 1989

DOI:https://doi.org/10.1103/PhysRevLett.64.115