Seeking Supernovas Systematically

Abstract

Since its discovery last February, Supernova 1987A has been much in the news. The unanticipated find is giving astronomers computer memories full of information (SN: 8/22/87, p.117 & 122), but as more and more details of the development of this nearby supernova become known, astronomers need a context in which to put them. Many aspects of the supernova have not been seen before, and astronomers wonder whether these are unique to it or common to a class or classes of supernovas. To tell the common from the uncommon, the usual from the anomalous about supernovas, astronomers need good statistical information about them. This will not come from nearby supernovas like 1987A. The odds against another blowing off as near to us as the Large Magellanic Cloud are probably too astronomical to calculate. Where the odds are good is in the random, more or less distant galaxies scattered over the sky To find a lot of supernovas to make up the statistical base, automated observational patrols, which were under development long before SN 1987A appeared, are now beginning to operate. Supernova action is not infrequent in the distant galaxies, when those galaxies are taken as a whole. As of Aug. 22, according to International Astronomical Union Circular 4441, the count had gone as far as SN 1987L, the twelfth supernova to be discovered this year. However, in the absence of automated patrols, most supernovas are found by accident during other investigations, as Ian Shelton of the University of Toronto found SN 1987A. And most discoveries are not as lucky as his. Usually a supernova is not noticed until its astrophysically most interesting period -its earliest days-are already past. According to Carl Pennypacker of the University of California at Berkeley, only 10 type II supernovas, which are in many respects the most interesting kind, have been discovered before their light output reached its maximum level. Astronomers would like to find supernovas before maximum light so that they can follow their development from as early an epoch as possible. At the recent Workshop on Instrumentation for Ground-Based Optical Astronomy, held at the University of California at Santa Cruz, Pennypacker and Sterling Colgate of New Mexico Institute of Technology in Socorro and Los Alamos (N.M.) National Laboratory described the supernova patrol programs that each of them leads.