Transcript: Quasars were mysterious when they were first discovered in the 1960s. But careful work showed that the quasar is surrounded by nebulosity, and eventually spectroscopy of the nebulosity showed that it was the light of stars in a normal galaxy. Thus quasar stands for quasi-stellar objects. They are not truly stellar but do show fuzz when observed with high resolution for example with the Hubble Space Telescope. Thus quasars are point-like nuclei in a host galaxy seen at large or cosmological distances. Quasars are normal galaxies with an extraordinarily luminous source of radiation in their centers. For example 3C273 is at a distance of six hundred megaparsecs or two billion lightyears. At its center is optical radiation with a power of ten to the power fourteen or a hundred trillion suns. This is an extraordinary amount of energy, and it emerges from a tiny region in the heart of the quasar.