Quasars and Collapsars: One Object, Two Personas

This paper examines the relationship between supermassive collapsars (black holes) and quasars. It shows that these are not different types of objects but the same physical object in different phases of activity. The passive phase — when little matter surrounds the collapsar — corresponds to an “ordinary” supermassive black hole (like Sagittarius A* in the center of the Milky Way). The active phase — when the black hole intensely accretes gas, dust, and stars — manifests as a quasar, the brightest beacon in the Universe, whose luminosity can exceed that of its entire host galaxy by hundreds of times. The mechanisms of accretion are discussed: infalling matter forms a hot accretion disk (millions of degrees) and relativistic jets — plasma streams ejected at nearly the speed of light over thousands of light years. Quasars play a key role in galaxy evolution as “cosmic architects”: their jets can either stimulate or suppress star formation. The paper illustrates the author‘s principle of the choice of the level of description (G): at the fundamental level (G₁) the object is a black hole with mass, spin, and charge; at the activity level (G₂) it is a quasar with an accretion disk and jets; at the cosmological level (G₃) it is a tool for studying the early Universe. Different levels of description give different but equally true pictures. The mistake would be to claim that a quasar is not a black hole. It is a black hole — simply one that is “eating.”