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 \over 2 } { pc } ) .
One finds an intensity in the line of 350 ^ { +350 } _ { -117 } photons cm ^ { -2 } sec ^ { -1 } , a wavelength of 905 \pm 7 \AA , and a width \sim 1 \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 .