Active Galaxies, Quasars, and Supermassive Black Holes (Astronomy)

Recall cards on active galactic nuclei and the supermassive black holes that power them. Quasars: the meaning of quasi-stellar radio source, their 1950s discovery with surplus radar gear, Maarten Schmidt's 1963 reading of the huge redshift of 3C 273, the redshifts that reach 96% of the speed of light, the Hubble Space Telescope host galaxies, and the rapid variability that pins the emitting region to a few light-months. The engine: a central black hole fed by a friction-heated accretion disk, the roughly 10% mass-energy efficiency that dwarfs nuclear fusion, masses from under a million to tens of billions of Suns, M87 and the 2019 Event Horizon Telescope shadow, and jets launched near light speed. And cosmic evolution: the early peak of quasars and star formation, the 1/200 black-hole-to-galaxy mass ratio, tidal disruption events, seed black holes, mergers such as NGC 6240, and black-hole feedback on star birth.