Supemovae remnants

In the early thirties of the last century Baade and Zwicky conjectured in their studies of supernova explosions that supemovae represent a transition from ordinary stars to compact objects, whose size is an order of magnitude smaller than the size of a white dwarf. At that time it was already known that the atomic nucleus consists of neutrons and it was clear that the density of the remnant objects must be of the same order as the nuclear density. Baade and Zwicky predicted that a supernova explosions will result in objects composed of closely packed neutrons (neutron stars). Prior to the beginning of the second World War (1939) a number of theoretical works by Landau, Oppenheimer, Volkoff and Snider showed, that indeed objects could exist with sizes about 10 km and masses about a solar mass. The density in these objects is about the nuclear saturation density and they basically consist of neutrons with a small amount of protons and electrons. The studies of neutron stars were subsequently stopped most likely due to the engagement of the nuclear scientists in the development of the nuclear bomb both in the West and the East. 

The strengths of the model are its natural connection to supemovae and star formation and that the supernova remnant would have enough time to form iron via the decay of nickel and cobalt to possibly produce the claimed iron lines. Moreover, it is expected to be a baryon-clean environment. The model is, however, very sensitive to the fine tuning of parameters. Moreover, GRB030329 places a rather strict limit of a few hours on the delay between the SN and the GRB and thus rules out the supranova model for at least this particular burst. 

It was Walter Baade who made the connection between the historical supernovae and the observed emission nebulae at their positions, thus identifying the remnants of the explosions. The most prominent object is of course the Crab Nebular (Messier 1), the leftover from the supernova in 1054 Baade 1942 May all Oort 1942. With extensive observations of bright supernovae Minkowski Minkowski 1941 introduced two subclasses. Zwicky Zwicky 1965 refined the classification scheme for supemovae further. However, for several decades only two main classes were maintained until in the early eighties it became clear that at least one further subclass needs to be added. 

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