Lecture 10: Black Holes and How They Shine Astronomy 5: The Formation and Evolution of the Universe Sandra M. Faber Spring Quarter 2007 UC Santa Cruz

Photon paths around objects of same mass and increasing density.

Baltimore seen through a strong gravitational lens

Approaching a black hole. R goes from 112RS down to 10 RS

Orbiting around a hole at 10 RS

We can use curved 2-d surfaces to model curved 3-d space The surfaces stand for the flat equatorial plane around a condensed object like a dense star or a black hole. Walking uphill (outwards) is analogous to moving radially outward from the dense object. Note that you walk a long way on the surface but the radius does not change very much. The usual formula of the circumference = 2R is wrong … the circumference is smaller than you expect. This is what we mean by “curved space.” Spacetime near a black hole Spacetime near a dense star

Wormholes are mathematical solutions to GR that may not actually exist Wormhole connecting two universes Wormhole connecting two spots in the same universe.

The centers of spheroids host massive black holes 3 billion M central black hole Relativistic “jet” of ionized plasma When gas falls onto BHs, they become active galactic nuclei (AGN) and quasars (QSOs) The famous active elliptical M87

Fly-in to the center of the M87 black hole

Artist’s conception of accretion disk with jet

Feedback generated by stellar mergers (QSO mode) Sources of “feedback” during a merger: • Gas is funneled into the central regions, fueling a starburst and creating a wind (Mihos & Hernquist 1994). • Orbital kinetic energy is converted to heat in cloud-cloud collisions, which drives a wind (Cox et al. 2005). QSO phase • Gas driven to the center fuels a black hole, creating a quasar (QSO) whose feedback quenches further infall and star formation (Hopkins et al. 2005).

Birth and death of a quasar during collision of two disk galaxies (gas only, stars not shown)