ASTRONOMY COLLOQUIUM (Greenstein Lecture)

Jesse Greenstein was there at the dawn of AGN, starting with a paper with Maartin Schmidt in 1964, the year I was born.  The normal stochastic variability of AGN was discovered almost immediately, and it now can be studied statistically with parameters that correlate with properties of the black hole such as mass.  Gravitational micro-lensing of lensed quasars and modern reverberation mapping campaigns can be used to explore the structure of accretion disks and the origin of this variability in detail. But modern synoptic surveys have also revealed an expanding zoo of other types of AGN variability.  There are tidal disruption events (TDEs), changing look quasars (and blazars!) and "anomalous nuclear transients".  We will tour this landscape, what we have learned and what happens next.