  Various recent observational developments are here used to make a more
critical analysis of the parameter space of the decaying neutrino theory for
the ionisation of the interstellar medium. These developments involve phenomena
inside our Galaxy, outside the Galaxy but at essentially zero red shift, and at
large red shifts. This new analysis leads to a viable theory with a decay
lifetime of $2{\pm}1\times 10^{23}$ sec, a decay photon energy of
$13.7{\pm}0.1$ eV, and a mass for the decaying neutrino of $27.4 {\pm}0.2$ eV.
  These parameters, when combined with some known astronomical quantities, lead
to predictions for the intensity, the wavelength and the width of the decay
line produced by neutrinos lying within one optical depth of the sun $({\sim}
1/2 pc)$. One finds an intensity in the line of $350^{+350}_{-117}$ photons
$cm^{-2} sec^{-1}$, a wavelength of $905\pm7\AA$, and a width $\sim1\AA$. These
predictions are relevant for the observations about to be made by the EURD
ultra-violet detector which is currently in Earth orbit on board the Spanish
MINISAT 01 satellite.
