  A lot of beautiful observations of Supernova remnant 1987A give a precise
idea of its structure and its evolution. The regular interpretations of the
observations set that the large energy needed to explain the brightness of the
pearl necklaces is provided by shock waves involving remnants of a first
explosion and a wave produced by the observed explosion although the existence
of this wave is discussed. We develop the alternative explanation of the
necklaces by photoionization. Our main hypothesis is that the explosion of the
blue supergiant progenitor produces two neutron stars and a central brilliant
object, a linear system similar to those which were observed by Halton Arp. We
suppose that these stars remains bright in extreme UV, to maintain the strong
ionization of a bubble of hot hydrogen nearly transparent in far UV (defined as
the range of Lyman frequencies of atomic hydrogen). Outside the bubbles, three
shells containing atomic hydrogen generate resonant, superradiant scatterings
at Lyman frequencies, in tangential competing modes. The superradiance cools
the gas and absorbs strongly the radial far UV light, hiding the stars. The
shells may be identified with the inner active shells found from light echoes.
