Pregalactic stars and the origin of the microwave background

Recently reported distortions in the spectrum of the microwave background have been interpreted as indicating that as much as 25 per cent of its energy content may be radiation generated by pregalactic stars and thermalized by dust grains. The fact that this fraction is so large motivates one to explore the possibility that the remaining 75 per cent may also have been generated by pregalactic stars, though at an earlier epoch when thermalization could have been achieved through free–free processes rather than by grains. This suggestion is not implausible since one would expect pregalactic stars to span a range of masses and the more massive ones would complete their nuclear-burning phase at an earlier epoch. However, energetic considerations require that the 75 per cent component be generated not by the massive stars themselves but by their black hole remnants. Before the black holes form, the Universe would be cold or tepid and this circumvents many problems associated with galaxy formation.