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Session 2 - Applied History of Astronomy II.
Oral session, Sunday, January 14
Salon del Rey Central, Hilton
Historical records of supernovae are of great value to modern studies of a variety of astrophysical problems, including: dynamics of supernova explosions; (2) formation of stellar remnants (neutron stars and/or black holes); and (3) behavior of the ejected material. For example, the date of the Crab supernova explosion as determined from the current expansion rate of the nebula assuming constant expansion velocity is A.D. 1140. By comparing this date with the historically recorded date of A.D. 1054, one immediately concludes that the nebula expansion rate must have been accelerating throughout the last nine centuries. Energy input from the subsequently discovered Crab pulsar neatly accounts for the difference between the two dates. Conversely, for Cassiopeia A, the kinematically determined date for the supernova explosion assuming constant expansion velocity (A.D. 1657) is earlier than the date for the event recorded by Flamsteed (A.D. 1680). Comparing these dates leads to the conclusion that the speed of the ejected gas must have been decreasing for much of the past three centuries. Combining the historical with the kinematical event dates allowed a dynamical determination of the mass of the ejecta to be made (10 - 12 Mo) which is in good agreement with estimates based on other observations, such as nebula x-ray emission (Brecher and Wasserman, 1980, Ap. J. Lett. 240, L105). Remarkably, historical records of the supernova explosions of A.D. 1006, 1572, and 1604 contain suggestions that each of these supernovae made a brief reappearance as an optical object in subsequent years. These historical records lead to the suggestion that Supernova 1987A might also reappear (Brecher, 1987, B.A.A.S., 19, 1102). The ejecta from the supernova explosion will impact an observed circumstellar shell, probably leading to significant optical, radio and x-ray emission, sometime during the next decade. If SN 1987A does indeed become optically brighter, perhaps it will also shed some light on the astrophysical origin(s) of the supernova reappearances which are found in the historical records.
