Effects of the Cosmic Neutrino Background Capture on Astrophysical Objects

Low-energy neutrinos from the cosmic background are captured by objects in the sky that contain material susceptible of single beta decay. Neutrons, which compose most of a neutron star, capture low-energy neutrinos from the cosmic neutrino background and release a high-energy electron in the MeV range. Also, planets contain unstable isotopes that capture the cosmic neutrinos. We show that this process is feasible and results in a non-negligible flux of electrons in the MeV range in neutron stars. We present a novel observable, the redshift evolution of the temperature of neutron stars due to neutrino capture, that could provide a route for detection of the cosmic neutrino background from future gravitational waves observatories. For planets the flux is significantly smaller and a measurement is not possible with currently envisioned technology. While the signature from neutron stars is small and challenging, it could result in a novel way to detect the cosmic neutrino background.