Transcript Ground-based Astronomy: Past, Present, and Future

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
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Approaching a black hole. R goes from 112RS down to 10 RS
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Orbiting around a hole at 10 RS
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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
When gas falls onto
The famous
BHs,active
they elliptical
become
active galactic
M87
nuclei (AGN) and
quasars (QSOs)
Relativistic “jet” of
ionized plasma
3 billion M central black hole
Fly-in to the center of the M87 black hole
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Artist’s conception
of accretion
disk with jet
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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).
QSO
phase
• Orbital kinetic energy is
converted to heat in cloud-cloud
collisions, which drives a wind
(Cox et al. 2005).
• 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)
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