It has often been suggested that the energy supply of a quasar is derived from a central body with a mass of 109−1010M⊙. However, it is known that such bodies have no stable and static equilibrium configurations beyond a relatively low degree of condensation. Only a very limited amount of energy can be extracted before instability sets in. Basically the instability is due to the dominance of radiation pressure in supporting the mass against its self-gravitation.

But if a massive object is in rapid rotation, then it is partly supported by centrifugal force, and is much less liable to an instability of this kind. It is therefore interesting to investigate the properties of a rotating disk-like object with a mass of the order of 109−1010M⊙, and to see whether its overall properties match those of any quasar. The most important parameters are 2σ0, the mass per unit area of the disk, and Z, its half-thickness. In the case of the quasar 3C 273 B, assumed to be at a distance of 450 Mpc, the most suitable pair of values are σ0 = 107 gm/cm2 and Z = 1016 cm.