Cosmic far-ultraviolet background radiation

It is demonstrated that interstellar dust grains forward-scatter far-ultraviolet radiation extremely strongly: the value of the Henyey-Greenstein scattering parameter g at 1425 A is shown to be at least 0.75; the actual value is very likely greater than 0.9. Also, observations of the Virgo cluster of galaxies sets a limit of tau greater than 2 x 10 to the 25th sec on the lifetime of 17-20 ev/C-squared heavy neutrinos, if such neutrinos are responsible for the gravitational binding of the cluster.