FAR-ULTRAVIOLET FLUORESCENCE OF MOLECULAR-HYDROGEN IN IC-63

We present observations of H-2 fluorescence at wavelengths between 100 0 and 1200 Angstrom from the bright reflection nebula IC 63. Observati ons were performed with the Berkeley spectrograph aboard the ORFEUS II mission. To the best of our knowledge, this is the first detection of astrophysical H-2 fluorescent emission at these wavelengths (excludin g planetary atmospheres). The shape of the spectrum is well described by the model of Sternberg. The absolute intensity, however, is fainter by a factor of 10 than an extrapolation from observations at longer u ltraviolet wavelengths. Of the mechanisms that might help to reconcile these observations, optical depth effects in the fluorescing H-2 itse lf are the most promising (or at least the most difficult to rule out) .