Upper limit on the mass of the electron neutrino

The historic detection by the Kamiokande-II collaboration¹ and the IMB collaboration² of neutrinos from the Large Magellanic Cloud (LMC) supernova provides the first opportunity to determine the mass, $m_{v_{\text{c}}}$, of the electron neutrino from astronomical observations. Here we show that $m_{v_{\text{c}}}$, is less than 11 eV, provided only that propagation effects have not conspired to sharpen, by more than a factor of two the narrow pulse-width of neutrinos, observed by the Kamiokande-II collaboration from the LMC supernova. This result improves on the laboratory limit on $m_{v_{\text{c}}}$ and confirms the view that electron neutrinos do not constitute the major component of the matter density of the Universe.