My understanding is that quasars are galaxies that are billions of light years away. Thus we see them as they were billions of years ago when they were much younger than our own galaxy & other galaxies nearby to us. The immense energy they emit is generated by matter falling into the central black hole that all galaxies have. So they have active centres. I assume as galaxies age then the black hole at the centre runs out of matter nearby to gobble up, with only the occasional passing objects such as stars randonly perturbed in that direction. I believe that our galaxy have reached this stage. Is it likely that all galaxies including our own were quasars when they were younger ?