Black holes

Rodrigo Nemmen
Black Holes
AGA5727 - Active Galactic Nuclei
Credit: ESO

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Hazard+14
Optical image of 3C 273
3C273, the first Quasar 7
Figure 6. The culmination of the Parkes positions and the Palomar redshift.
3C273 had become:
eve
tern
he w
ligh
of c
hav
him
and
On
tha
also
Ha
tha
Thu
star
hig
obj
was
the
per
Qu
in a
Soc
and
tan
app
oth
rep
the
The
are
Maarten Schmidt was the fi rst to
recognize that quasars are ultra-
luminous distant objects. After
Cyril Hazard and his colleagues in
Australia had pinned down the
position of the radio source 3C 273,
Schmidt took a spectrum of the
starlike object in that location.
The unusual features of the spec-
trum could be understood only if
there was a 16 percent redshift,
implying an enormous distance.
Schmidt has, over the past 40
years, continued to discover and
study distant quasars. He has
been a leader in analyzing how
the quasar population depends
on redshift (or cosmic epoch), as
described in Chapter 9.
mber 29 he managed to obtain a spectrum of the “star” that was not over-
which showed some faint emission lines, but with no obvious explanation
y expected stellar lines.
yed until February 6th, as outlined in the paper presented to the American
Society (Schmidt, 2011). He wrote:
d on 6 February 1963. In response to Hazard’s letter I decided to have
at the spectra... For reasons that I don’t remember I tried to construct an
iagram. When the energy levels did not come out regularly spaced, I was
check on the regularity of the observed lines, I decided to compare them
er lines of hydrogen... Specifically, I took for each line in 3C 273 the ratio
gth over the wavelength of the nearest Balmer line. The first ratio was 1.16,
s... also 1.16.
ruck me that I might be seeing a redshift. When the third and fourth ratios
e to 1.16, it was abundantly clear that I was seeing in 3C 273 a redshifted
um.”
ed fortunate that the 3C273 redshift was small enough that the Balmer
re and would be readily recognised.
aarten Schmidt’s 200” spectrum taken on the night of December 29, with the

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Quasars in the centers of distant galaxies (z>1)
outshine all stars in the host galaxy
this image: z ~ 0.2
d
L
~ 1 Gpc
Hubble Space Telescope
Bahcall+97

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THE ASTROPHYSICAL JOURNAL, 479:642È658, 1997 April 20
1997. The American Astronomical Society. All rights reserved. Printed in U.S.A.
(
HUBBL E SPACE T EL ESCOPE IMAGES OF A SAMPLE OF 20 NEARBY
LUMINOUS QUASARS1
JOHN N. SOFIA AND DAVID H.
BAHCALL, KIRHAKOS, SAXE
Institute for Advanced Study, School of Natural Sciences, Princeton, NJ 08540
AND
DONALD P. SCHNEIDER
Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802
Received 1996 August 21; accepted 1996 November 8
ABSTRACT
Observations with the Wide-Field Camera of the Hubble Space Telescope (HST ) are presented for a
representative sample of 20 intrinsically luminous quasars with redshifts smaller than 0.30. These obser-
vations show that luminous quasars occur in diverse environments that include ellipticals as bright as
the brightest cluster galaxies (two), apparently normal ellipticals (10), apparently normal spirals with H II
regions (three), complex systems of gravitationally interacting components (three), and faint surrounding
nebulosity (two). The quasar host galaxies are centered on the quasar to the accuracy of our measure-
ments, 400 pc. There are more radio-quiet quasars in galaxies that appear to be ellipticals (seven) than in
spiral hosts (three), contrary to expectations. However, three, and possibly Ðve, of the six radio-loud
quasars have detectable elliptical hosts, in agreement with expectations. The luminous quasars studied in
this paper occur preferentially in luminous galaxies. The average absolute magnitude of the hosts is 2.2
mag brighter than expected for a Ðeld galaxy luminosity function.
The superb optical characteristics of the repaired HST make possible the detection of close galactic
companions; we detect eight companion galaxies within projected distances of 10 kpc from quasar
nuclei. The presence of very close companions, the images of current gravitational interactions, and the
higher density of galaxies around the quasars suggest that gravitational interactions play an important
role in triggering the quasar phenomenon.
Subject headings: galaxies: clusters: general È galaxies: interactions È galaxies: structure È
quasars: general
1. INTRODUCTION
Figures and (Plates 25È28) tell the main story of this
1 2
paper. We urge the reader to look at these beautiful HST
images before continuing with the text and the quantitative
details.
point-spread function (PSF), there are small, quantitative
di†erences between the results described in this paper and
previous results we have reported. In the previous work, we
used a stellar PSF determined from a red standard star,
F141. In the present work, we have used stellar PSFs that
ABSTRACT
Observations with the Wide-Field Camera of the Hubble Space Telescope (HS
representative sample of 20 intrinsically luminous quasars with redshifts smaller t
vations show that luminous quasars occur in diverse environments that include
the brightest cluster galaxies (two), apparently normal ellipticals (10), apparently n
regions (three), complex systems of gravitationally interacting components (three),
nebulosity (two). The quasar host galaxies are centered on the quasar to the acc
ments, 400 pc. There are more radio-quiet quasars in galaxies that appear to be el
spiral hosts (three), contrary to expectations. However, three, and possibly Ðve,
quasars have detectable elliptical hosts, in agreement with expectations. The lumin
this paper occur preferentially in luminous galaxies. The average absolute magnit
mag brighter than expected for a Ðeld galaxy luminosity function.
The superb optical characteristics of the repaired HST make possible the dete
companions; we detect eight companion galaxies within projected distances of
nuclei. The presence of very close companions, the images of current gravitationa
higher density of galaxies around the quasars suggest that gravitational interacti
role in triggering the quasar phenomenon.
Subject headings: galaxies: clusters: general È galaxies: interactions È galaxies: st
quasars: general
1. INTRODUCTION
Figures and (Plates 25È28) tell the main story of this
1 2
paper. We urge the reader to look at these beautiful HST
images before continuing with the text and the quantitative
details.
We summarize in this paper the results of our analysis of
HST -WFPC2 observations of a representative sample of 20
point-spread function (PSF
di†erences between the resu
previous results we have rep
used a stellar PSF determ
F141. In the present work,
were obtained for four se
cussion in of the PSFs c
° 4
The visual appearanc
1996).

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The pioneers of the theory of supermassive black holes
applied to AGNs: Salpeter, Zeldovich, Lynden-Bell
Chapter 5
fueled by the transfer of gas from the companion star onto the compact
remnant, the massive black holes in AGN would be fueled through the
capture of gas from the surrounding galaxy, or even by the swallowing
of entire stars. This captured debris would swirl downward into the
intense gravitational fi eld, reaching nearly the speed of light before it is
swallowed. The gravitational energy thus liberated would provide the
power for both the luminosity and the outfl owing gaseous jets that char-
acterize AGN. Lynden-Bell also predicted that the modern-day galaxies
that had once hosted quasars should still contain their black hole relics.
Evidence for these quiescent black holes now abounds (Chapter 8), pro-
viding perhaps the strongest vindication of the black hole paradigm.
Modeling Quasars
Salpeter
Zeldovich
Lynden-Bell

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Powerful, relativistic jets from galactic nuclei
Signs of Activity
to a precision of a few arcseconds, by noting the time at which it was
occulted by the Moon. They had to make special adjustments to the
telescope to observe something as far north – and consequently as
close to the horizon – as 3C 273. (“3C” denotes the third Cambridge
catalog of radio sources – the source had been discovered by means
The Very Large Array in New
Mexico reveals the double-lobed
radio structure of Cygnus A in rich
detail. The energy produced in
the nucleus is carried to the lobes
by jets, the traces of which are
Remain aligned for millions of years (what is the gyroscope?)

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Spectral energy distributions are decisively non-stellar
Ho 04

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Hard X-ray sources in the galactic nuclei
NASA, CXC, Hickox+

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0
0 −30
30 −60
60 −90
90 −120
120 −150
150 −180
180
30
−30
60
−60
90
−90
90
Ackermann+15,
1501.0605
Gamma-ray sky observed by Fermi LAT is
dominated by blazars
FSRQs: ﬂat spectrum radio quasars
BL Lac objects
AGNs of unknown type
non-blazar AGNs

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“Modern” times

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Keplerian rotation curves: signature of motion
around a central mass

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Keplerian rotation curves: signature of motion
around a central mass
v =
r
GM
r

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SUPERMASSIVE BLACK HOLE OF M87 581
sitions of the slit during the observations compared with the Ha
] N II image of the M87 disk from the WFPC2 archive. The gray levels are
d 40% of the nuclear peak in the outer region. The nucleus has been rescaled to be displayed within this range of values. North is up and east is
n, geometric distortion is also induced on the slit and dispersion directions by the spectrographic mirror and the
distortion in the dispersion direction was determined by tracing the spectra of two stars taken in the core of the
globular cluster. These stars are ^130 pixels apart and almost at the opposite extremes of the slit. The distortion
t direction was determined by tracing the brightness distribution along the slit of the planetary nebula NGC 6543
es. Ground-based observations (Perez, Cuesta, Axon, & Robinson, in preparation) indicate that the distortion
TABLE 1
LOG OF OBSERVATIONS
Integration Time
Target Data Set Date (1996) (s) Format Description
M87 . . . . . . . . . . . . . X3E40101T Jul 25 297 1024 ] 512 Interactive acq.
M87 . . . . . . . . . . . . . X3E40102T Jul 25 2169 1024 ] 512 Spectrum =POS1
M87 . . . . . . . . . . . . . X3E40103T Jul 25 600 1024 ] 512 Internal Ñat
M87 . . . . . . . . . . . . . X3E40104T Jul 25 600 1024 ] 512 Internal dark
M87 . . . . . . . . . . . . . X3E40105T Jul 25 2169 1024 ] 512 Spectrum 1 =NUC
M87 . . . . . . . . . . . . . X3E40107T Jul 25 2169 1024 ] 512 Spectrum =POS2
M87 . . . . . . . . . . . . . X3E40109T Jul 25 2597 1024 ] 512 Spectrum 2 =NUC
M87 . . . . . . . . . . . . . X3E4010AT Jul 25 600 1024 ] 512 Internal Ñat
M87 . . . . . . . . . . . . . X3E4010BT Jul 25 2597 1024 ] 512 Spectrum 3 =NUC
M87 . . . . . . . . . . . . . X3E4010CT Jul 25 600 1024 ] 512 Internal Ñat
M87 . . . . . . . . . . . . . X3E4010DT Jul 25 2597 1024 ] 512 Spectrum 4 =NUC
No. 2, 1997 SUPERMASSIVE BLACK HOLE OF M87
FIG. 12.ÈBest Ðts of the observed rotation curve with the Keplerian thin disk model. The solid line corresponds to cpix \ 22
km s~1 and the dotted line to cpix \ 22.7,
1.73 ] 109 M
_
, h
\ 0¡
.7, i \ 49¡V
sys
\ 1204 b \ 0A
.06, M
BH
(sin i)2 \ 1.68 ] 109 M
_
km s~1 (s
2 \ 1.73). The residuals are computed for the former set of values and the error bars on the velocity are the square ro
1274
eq. (9).
Macchetto+97, ApJ
Keplerian
rotation
curve
Kinematics of gaseous disk in giant elliptical
galaxy M87 mapped with HST
M = 3 ⇥ 109 M
v =
r
GM
r

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VLBA radio observations of water maser in NGC
4258: thin gas disk following Keplerian motion
Kormendy & Ho 2013, ARA&A
M = 3.6 ⇥ 107 M
Myioshi+95, Nature
Observer’s view
Top view
High
Bowl
0.1 pc
0.1 pc
–1
1,200
1,000
800
600
0
0 20,000 40,000
NGC 4258
Keplerian rotation curve
60,000 80,000
1 2 3 4
Impact parameter (mas)
r/rS
(km s–1)
5 6 7 8 9
Redshifted masers
Blueshifted masers
Systemic masers
a
b
ded by Universidade de Sao Paulo (USP) on 04/30/15. For personal use only.
2-Kormendy ARI 24 July 2013 12:27
Observer’s view
Top view
High
Bowl
0.1 pc
0.1 pc
–1
1,200
1,000
800
600
400
200
0
0.1 0.2 0.3
0.0
0
0 20,000 40,000
NGC 4258
Keplerian rotation curve
60,000 80,000
1 2 3 4
Impact parameter (mas)
r/rS
r (pc)
Velocity (km s–1)
5 6 7 8 9
Redshifted masers
Blueshifted masers
Systemic masers
a
b

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VLBA radio observations of water maser in NGC
4258: thin gas disk following Keplerian motion

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ESO
Journey to Our Galactic Center

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10 light-days = 260 billion km
Ghez, Schödel, Genzel et al.
central mass =
4 million solar masses
Resolved stellar dynamics around Our Galactic
Center with Keck observations

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black
hole
Our Galactic Center hosts the nearest
supermassive black hole: Sagittarius A*
Ghez, Schödel, Genzel et al.
central mass =
4 million solar masses
10 light-days = 260 billion km

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Using stars as test particles to probe the central
mass: stellar kinematics
van den Bosch+12, Nature
relation16 predicts a black-hole mass of 2.4 3 109M8
, so the measured
value is almost one order of magnitude higher, or a 2.1-s.d. outlier
relative to the intrinsic scatter in the M.
–s relation1.
Apart from NGC 1277, NGC 4486B9 and
to lie significantly above the relations, and a
known to lie significantly below the relatio
know if these over-massive and under-mass
the tails of a relatively narrow distribution o
properties, or if they demonstrate non-un
more black-hole measurements, including th
pact galaxies with high velocity dispersions, w
the cause of the black-hole/galaxy connectio
–300
–200
–100
0
100
200
300
V (km s–1)
a 17 × 109M
O
black hole
1 × 108M
O
black hole
NGC 1277
100
200
300
400
σ (km s–1)
Seeing
b
–0.2
0.0
0.2
h
3
c
–6 –4 –2 0 2 4 6
x (kpc)
–0.2
0.0
0.2
d
.
.
h
4
we construct a three-dimensional luminous-mass model of the stars by
107
108
109
1010
1011
Black-hole mass (M
O
)
NGC
NGC 4486B
Ref. 8
Ref. 19
Ref. 16
Mass–luminosity
.
Modeling:
Disentangle
gravitational contribution
of host galaxy vs central
“invisible” mass
Every galaxy with a
bulge has a
supermassive invisible
object in its center

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60 80 100 200 300 400
Velocity dispersion / km s-1
106
107
108
109
1010
M
BH
/ M
sun
Elliptical / classical bulge
Pseudo-bulge
, AGN
, Quiescent
Galaxies somehow coevolve with their central
black holes: the M-σ relation
Woo+13
central black hole
host galaxy property

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Schimoia, …, Nemmen+12
The Astrophysical Journal, 748:145 (12pp), 2012 April 1 Schimoia et al.
Figure 1. Acquisition image from 2010 August 15, where we illustrate the
locations of the 1.
′′0 × 1.
′′0 extraction windows for the nucleus and stellar
population spectra. The square labeled A represents the nuclear extraction
window, while squares B and C represent the extranuclear ones, from which we
obtained the spectrum of the underlying stellar population.
(A color version of this figure is available in the online journal.)
continuum to the corresponding value at the nucleus) thus
Figure 2. Observation from 2010 August 15. Top: nuclear spectrum (region A of
Figure 1). Middle: stellar population obtained from averaging the spectra from
regions B and C in Figure 1. Bottom: nuclear spectrum after the subtraction of
the stellar population.
blue continuum we need the FC continuum to contribute with
at least 15%–20% of the flux at 5800 Å. We thus can say that a
possible FC contribution to the nuclear spectrum is lower than
20% of the continuum flux at 5800 Å. We consider this value
an upper limit, as a comparison between the stellar continuum
from our spectra and the AGN continuum obtained in the work
of Nemmen et al. (2006) shows that the stellar continuum in our
FWHM ≈ 10000 km/s
center distance of the ring (from 1
¼ 1300 to 450) could
lead to the observed increase in the separation of the two
peaks, R
ÀB
. Such a dramatic change in the physical loca-
tion of a given volume of gas could not occur on a timescale
of 5 yr, however, as we noted in x 4.1. Rather, the emission
properties of the ring must have changed, so that the radius
of maximum emission became smaller. Therefore, to pro-
duce a self-consistent and physically plausible scenario for
the entire set of observations, we were led to revise the
model parameters. This revision represents a refinement of
earlier models, which is possible only after following the
variability of the line profile over a baseline of 10 yr. We
now propose that the ring has always had a smaller inner
radius of 1
¼ 450 (and now resembles a disk more than a
ring) and that the increasing width of the profile is due to a
change in emissivity such that, in more recent epochs, the
inner regions of the disk make a more significant relative
contribution to the total line emission. This picture is also
consistent with the observational result that the flux of the
broad line is decreasing, as discussed above.
To explain the increasing separation between the two
peaks, we experimented with several emissivity laws. We
found that we could best reproduce the observations with a
broken power law, such that inside a radius q the power-
law index is q1
¼ À1 and outside this radius q2
¼ 1. This
means that the emissivity increases with radius from 1 to q
and then decreases with radius beyond q. These q-values
are also physically motivated: in the ‘‘ saturation ’’ region,
the increase in emissivity is due to the increase in the area of
the ring, while beyond q, the decrease can be understood as
due to both the drop-off in the intensity of the radiation field
as rÀ2 and the increase of the emitting area as r.
In this parameterization of the disk emissivity, varying
the ‘‘ break radius ’’ q
allows us to reproduce the shifts of
the blue and red peaks. In particular, allowing the break
radius to decrease with time shifts the region of maximum
emission closer to the center and results in an increase in the
separation between the two peaks. At the same time, since
2 Nov. 91
5 Oct. 92
5 Jan. 94
6 Dec. 94
24 Jan. 96
24 Sep. 97
6400 6600 6800
0
1
2
3
4
Fig. 7.—Fits of the elliptical-disk model to the profiles from 1991
November to 1997 September obtained by changing only 0 (the
orientation of the disk relative to the line of sight) and q (the radius of the
peak of the emissivity law). The values of these parameters are listed in
Table 3.
Storchi-Bergmann,
Nemmen+03
Broad, mildly relativistic emission lines in the
optical

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Tanaka+95, Nature
Broad, relativistic velocities from X-ray emission
lines: produced within a few Schwarzschild radii
FWHM ≈ 100.000 km/s

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Broad, relativistic velocities from X-ray emission
lines: produced within a few Schwarzschild radii

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Black Holes

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A few classics on general relativity and black
holes

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Event horizon

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s of light rays become
rved close to the
a black hole. As the
pproached, a light
be aimed within an
y narrow cone in order
ing dragged into the
Schwarzschild radii a
med light beam can
ack hole indefi nitely.
zon, the escape cone
no light rays emit-
is radius can avoid
ed into the black hole.
rom just outside the
ild radius would reach
bserver with a large
nd a clock near the hole
ear to run slow.
Begelman & Rees

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Para a Terra virar um
buraco negro:
Raio = 1 cm

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Buraco negro com a massa
do Sol: 300000 MTerra
Raio = 3 km

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Thorne
Radii of different objects with M = 1.2 MSun. Black
holes are the most compact objects in nature
white dwarf
neutron
star
black hole

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General relativistic effects: Observer
approaches a Schwarzschild black
hole, keep in communication with
another observer far away

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STSCI

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-1.0 -0.5 0.0 0.5 1.0
j =
a
M
1.0
1.2
1.4
1.6
1.8
2.0
R+
Event horizon radius as a function of spin

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Kerr black holes drag space around them within a
region called ergosphere
frame-dragging or Lense-Thirring effect

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Depiction of the ergosphere (static limit)

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Thorne

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Goldstein
Effective potential for the central force problem
in Newtonian physics

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Misner, Thorne & Wheeler
Effective potential for orbits around a
Schwarzschild black hole

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Black holes have an innermost “danger zone”:
particles cannot orbit anymore for rRisco
j = a/M = 0

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Black holes have an innermost “danger zone”:
particles cannot orbit anymore for rRisco = RH
j = a/M = 1

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UO
aim
o 0.2 0.5 0.7 0.6 0.9 0.95 0.96 1
mO.
(3.12)
Fig.3.2. Efficiency of energy release by gas accreting through a thin accretion disk onto
a spinning black hole. The quantity plotted is 1 - em. as a function of the hole angular
efﬁciency of
energy release
Blandford

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20 40 60 80 100
0.15
0.20
0.25
Circular speed
M = 108 Msun
vK/c
R/RS
Schwarzschild black hole

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A cloud of interstellar gas is rotating slowly around its axis and
contracting because of the attractive pull of its own gravity. As the
cloud collapses, it rotates faster.
The gas in the cloud’s equatorial plane moves inward more slowly
because its rotation starts to balance the gravity. Gas above and
below the plane falls inward much faster.
Gravitational
contraction
Rotation
Faster
contraction
Slower
contraction
galaxy. In general, galaxies do not
tic collisions and mergers compli-
At least some elliptical galaxies, as
of spiral galaxies, may have arisen
m in binary star systems when one
compact, dense white dwarf) grav-
companion (usually a larger, less
considerable angular momentum
otion of the two stars around their
it typically cannot fall directly in-
arf. Instead the gas ends up form-
.
ch shorter year than Earth—a mere
nner parts of a disk invariably takes
bit than does material in the outer
al periods causes shear: bits of ma-
stances from the center of the disk
ox on page 54]. If some form of fric-
erial, it tries to slow down the more
s and speed up the more slowly or-
ar momentum is therefore trans-
outer regions of the disk. As a con-
ner regions loses rotational support
ard. The overall result is a gradual
he central star or black hole.
to the innermost orbit of an accre-
avitational potential energy. Some
into giving the material the faster
ls inward; the rest is dissipated into
y by the friction itself. Thus, the ma-
very hot, emitting copious amounts
ay radiation. The energy release can
dable power sources.
Gravitational
contraction
Rotation
Faster
contraction
Slower
contraction
of the stars (for example, a compact, dense white dwarf) grav-
itationally pulls gas off its companion (usually a larger, less
compact star). This gas has considerable angular momentum
from the original orbital motion of the two stars around their
common center of mass, so it typically cannot fall directly in-
ward toward the white dwarf. Instead the gas ends up form-
ing a disk around the dwarf.
Just as Mercury has a much shorter year than Earth—a mere
88 days—the material in the inner parts of a disk invariably takes
less time to complete one orbit than does material in the outer
parts. This gradient in orbital periods causes shear: bits of ma-
terial at slightly different distances from the center of the disk
slide past one another [see box on page 54]. If some form of fric-
tion is present in the disk material, it tries to slow down the more
rapidly orbiting inner regions and speed up the more slowly or-
biting outer regions. Angular momentum is therefore trans-
ported from the inner to the outer regions of the disk. As a con-
sequence, material in the inner regions loses rotational support
against gravity and falls inward. The overall result is a gradual
spiraling of matter toward the central star or black hole.
As material spirals down to the innermost orbit of an accre-
tion disk, it must give up gravitational potential energy. Some
of the potential energy goes into giving the material the faster
orbital speed it gains as it falls inward; the rest is dissipated into
heat or other forms of energy by the friction itself. Thus, the ma-
terial in the disk can become very hot, emitting copious amounts
of visible, ultraviolet and x-ray radiation. The energy release can
make accretion disks formidable power sources.
This phenomenon is what ﬁrst alerted astronomers to the ex-
istence of black holes. Black holes themselves cannot emit light,
but the accretion disks around them can. (This general statement
ignores the theorized Hawking radiation, an emission that
would be undetectable for all but the smallest black holes and
JIAN
Rotation
Faster
contraction
Slower
contraction
Blaes, SciAm

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Credit: ESO

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Black holes

Black holes

Rodrigo Nemmen

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