How long is a Quasars life and what happens when it dies?
The question you asked about quasar lifetimes is an excellent one, but we only know this on the basis of theoretical arguments that are consistent with observational data; all quasars ever discovered (the first discovery was about 35 years ago) are still “there,” so this is the only truly undisputed observational measurement of their lifetime. Let me describe what we know about quasars, and from this, I will give you some arguments for their lifetimes. In general, quasars are relatively bright point sources; we believe that they are centers, or “nuclei” of galaxies. They show large redshifts, meaning that they are moving away from us at large velocities. In the currently accepted scenario that the Universe is expanding such that the velocity of expansion is roughly proportional to the distance from us to an object, this means that quasars are very distant objects, located often 1/2 way to the edge of the visible Universe. Two points are important here: First, since quasars are relative
