Radiation Pressure Supported Stars in Einstein Gravity

Even when we consider Newtonian stars, i.e., stars with surface gravitational redshift, z ≪ 1, it is well known that, theoretically, it is possible to have stars, supported against self-gravity, almost entirely by radiation pressure. However, such Newtonian stars must necessarily be supermassive(Weinberg 1972).We point out that this requirement for excessive large M , in Newtonian case, is a consequence of the occurrence of low z ≪ 1. On the other hand, if we remove such restrictions, and allow for possible occurrence of highly general relativistic regime, z ≫ 1, we show that, it is possible to have radiation pressure supported stars at arbitrary value of M . Since radiation pressure supported stars necessarily radiate at the Eddington limit, in Einstein gravity, they are never in strict hydrodynamical equilibrium. Further, it is believed that sufficiently massive or dense objects undergo continued gravitational collapse to the Black Hole stage characterized by z = ∞. Thus, late stages of Black Hole formation, by definition, will have, z ≫ 1, and hence could be examples of quasi-stable general relativistic radiation pressure supported stars. (Mitra 2006). It is shown that the observed duration of such Eddington limited radiation pressure dominates states is t ≈ 5 × 10(1 + z) yr. Thus, t → ∞ as Black Hole formation (z → ∞) would take place. Consequently, such radiation pressure dominated extreme general relativistic stars become Eternally Collapsing Objects and the BH state is preceded by such an eternal radiation pressure supported phase.