On Matter Confined by Radiation Pressure

Active Galactic Nuclei (AGN) can produce steady state luminosity which far exceeds the luminosity ofa whole galaxy. Observations indicate dilute gas which is present close to the massive black hole which resides at the centre of AGN. The energy transmitted from the radiation to the gas is well studied, but the momentum transfer did not receive much attention. I will describe the universal structure induced by the incident radiation pressure, and how it can naturally explain a host of emission and absorption properties of the ambient gas. Possible relevance to other systems will be briefly mentioned.