THE VISIBILITY OF GALACTIC SUPERNOVAE

We have obtained the distribution of the apparent visual magnitudes of galactic supernovae by integrating the interstellar absorption along the lines of sight to a large number of randomly positioned events. We find that over 70% of supernovae in the Milky Way never reach naked e ye visibility, and that more than half are fainter than V = 13 at maxi mum light. On the assumption that the historical record is complete fo r V less than or equal to 0, we infer that supernovae occur in the Gal axy at a rate of about 3 per century, and that the first 600 years of the present millenium may have been a period of unusually high superno va activity. The probability p that no galactic supernova has been see n in the last 100 years is calculated for a range of assumptions about the threshold magnitude for assured discovery; we consider that p gre ater than or similar to 0.6 is not unlikely.