QUASARS, DUST AND GALACTIC CENTRE

The black-hole model of galactic nuclei is used to discuss properties of quasars as proto-black-holes in the middle of galaxies. Quasar life-times may be as long as ~ 10 8 years and masses will be of the order of 10 8 M 0. Dust in the neighbourhood of black holes is sometimes driven from the accreted gas by radiation pressure. This may cause the dust often seen in exploding nuclei and the infra-red radiation from the galactic centre. Dust models for the galactic centre are considered in detail, and it is suggested that there may be a central black hole currently emitting ~ 1·5 x 10 8 L O in the ultra-violet and blowing away a hot nuclear wind. Emission knots in the central regions probably contain prominent OB stars which would make the Galaxy later than Sb. Finally we list critical observations which could establish the existence of a large central mass in the Galaxy of so small a size that it must be associated with a black hole. © Royal Astronomical Society.