Quasars

Quasars are peculiar objects that radiate as much energy per second as a thousand or more galaxies, from a region that has a diameter about one millionth that of the host galaxy. Indeed, some quasars are smaller than the size of standard solar systems.

When compared to active galaxies, quasars exhibit many of the same properties. Radiation is nonthermal and some are observed to have jets and lobes like those of radio galaxies. Quasars are intense sources of X-rays as well as visible light. They are the most powerful type of X-ray source yet discovered. They can be observed in many parts of the electromagnetic spectrum including radio, infrared, optical, ultraviolet, X-ray and even gamma rays, while most quasars are found to emit in the infrared. Some quasars are so bright that they can be seen at a distance of 12 billion light years.

The power of a quasar depends on the mass of its central supermassive black hole and the rate at which it swallows matter. Almost all galaxies, including our own, are thought to contain supermassive black holes in their centers. Quasars represent extreme cases where large quantities of gas are pouring into the black hole so rapidly that the energy output is a thousand times greater than the galaxy itself.