Question: where does the energy emitted by agn and quasars come from

title: Quasar
text: Various explanations were proposed over time . It was suggested , for example , that the redshift of quasars was not due to the expansion of space but rather to light escaping a deep gravitational well . However a star of sufficient mass to form such a well would be unstable and in excess of the Hayashi limit . Quasars also show forbidden spectral emission lines which were previously only seen in hot gaseous nebulae of low density , which would be too diffuse to both generate the observed power and fit within a deep gravitational well . There were also serious concerns regarding the idea of cosmologically distant quasars . One strong argument against them was that they implied energies that were far in excess of known energy conversion processes , including nuclear fusion . At this time , there were some suggestions that quasars were made of some hitherto unknown form of stable antimatter and that this might account for their brightness . Others speculated that quasars were a white hole end of a wormhole , or a chain reaction of numerous supernovae .