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The end-point evolution of a self-gravitating cluster of stars or a galactic nucleus is shown to result in the coalescence of stars to form massive ones necessarily before energetic collisions can disrupt them. The rapid evolution of the resulting massive stars (limited to Mo) gives rise to a maximum supernova rate in equilibrium with the cluster coalescence rate of 5-10 supernovae per year. The kinetic energy of the mass ejected by these supernovae ( times the usual observed optical emission) is converted into heat by the collision with a gas cloud which is determined by the cluster gravitational field and the rate of supernovae. The gas-cloud thickness is approximately one Compton scattering mean free path (R 10' cm, p = 2 >c 10- gm/cm3). The principal optical emission occurs due to inverse Compton cooling of the electrons heated by the collisional dynamic friction of the matter ejected from the supernova at lower velocity. The higher-velocity fraction penetrates and escapes to a lower-density gas region, there exciting counter-streaming plasma oscillation of large amplitude. A new mechanism for radio emission occurs whereby the photons emitted by electrostatic bremsstrahlung (analogous to synchrotron emissions) are multiply scattered from the coherent plasma oscillations. These photons diffuse in momentum space to much higher frequencies before escaping. The resulting optical and radio emission spectra, magnitude, and fluctuations are in agreement with the Hubble Doppler shift interpretation of quasi-stellar observations.
Stirling A. Colgate (Sun,) studied this question.