Transcript Power Point Presentation - Fermi Gamma

Astronomy 350
Cosmology
Professor Lynn Cominsky
Department of Physics and Astronomy
Offices: Darwin 329A and NASA EPO
(707) 664-2655
Best way to reach me:
[email protected]
February 25, 2003
Lynn Cominsky - Cosmology A350
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Black Holes and Cosmology
 BH are a possible endpoint of stellar
evolution (from very massive stars)
 BH warp space and time around them,
thereby affecting the evolution of the galaxies
 Central BH in galaxies may be the seeds that
formed the galaxies and may be the only
things left in the galaxies at the end of time
 Central BH in galaxies are signposts that help
us find the earliest galaxies
February 25, 2003
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White Dwarfs, Neutron Stars and
Black Holes
 White dwarfs are the size of the Earth
and about 1 Mo
 Neutron stars are 10 km in radius and
about 1.4 Mo
 One teaspoon of NS material weighs
100 million tons!
 After supernova, if cores are larger than
3 Mo , a black hole will be formed
February 25, 2003
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Masses of Black Holes
 Primordial – can be any size, including very small




(If <1014 g, they would still exist)
“Stellar mass” black holes – must be at least 3 Mo
(~1034 g) – many examples are known
Intermediate black holes – range from 100 to 1000
Mo - located in normal galaxies – many seen
Massive black holes – about 106 Mo – such as in
the center of the Milky Way – many seen
Supermassive black holes – about 109-10 Mo located in Active Galactic Nuclei, often
accompanied by jets – many seen
February 25, 2003
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Black Hole Structure
 Schwarzschild radius
defines the event
horizon
 Rsch = 2GM/c2
 Not even light can
escape, once it has
crossed the event
horizon
 Cosmic censorship
prevails (you cannot see
inside the event horizon)
February 25, 2003
Schwarzschild BH
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The First Black Hole
 Cygnus X-1
binary system
 Most likely mass
is 16 (+/- 5) Mo
 Mass determined
by Doppler shift
measurements of
optical lines
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Journey to a black hole
 This video is slightly out of date – new
NASA missions are now being
considered instead of ARISE
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Binary star systems
 Often stars are formed in binary systems
 Since they have unequal masses, the more
massive star will evolve faster - and reach the
end of its main sequence lifetime
 In some cases, the supernova of the primary
star will not disrupt the binary system and a
COMPACT BINARY is formed
 Mass transfer can then occur from the main
sequence star onto the collapsed, compact
companion star - which can be a WHITE
DWARF, NEUTRON STAR or BLACK HOLE
February 25, 2003
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X-ray Binary movie
February 25, 2003
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Measuring Mass
 At least 6 stellar
mass BH exist in
our galaxy
 Easiest to
measure Doppler
shift accurately
when X-rays are
not heating the
accretion disk
 X-ray “novae”
February 25, 2003
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Rossi X-ray Timing
Explorer
 Launched in 1995 – still operational
 Large area X-ray detectors to study timing
details of material falling into black holes or
onto the surfaces of neutron stars
February 25, 2003
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“Old Faithful” Black Hole
movie
 Binary black hole
system known as
“microquasar”
 Regular X-ray
outbursts
discovered with
RXTE
 Outbursts are linked
to appearance of IR
jets
February 25, 2003
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Milky Way’s Black Hole
 Best evidence comes from
infrared measurements of stellar
motion in central Milky Way by
Ghez et al. and Genzel et al.
 S2, the closest star to Sgr A*
(the radio source at the exact
center of the Milky Way)
indicates a mass of 2.6 million
+/- 0.2 Mo
 S2 is at a distance of 17 lighthours from Sgr A* - whose event
horizon is 26 light seconds
February 25, 2003
Lynn Cominsky - Cosmology A350
movie
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NGC 4261 – best HST photo
 100 million light
years away
 1.2 billion Mo black
hole in a region the
size of our Solar
System
 Mass of disk is
100,000 Mo
 Disk is 800 light
years across
February 25, 2003
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Chandra X-ray Observatory
 Launched on July 23, 1999, it
is the “Hubble” of X-ray
astronomy – best images
ever!
 Named after Subrahmanyan
Chandrasekhar - Nobel
prize winner who worked out
the upper mass limit for white
dwarfs (among many other
things)
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Chandra finds black holes are
everywhere!
Deep Image
Empty
Black holes in empty
space
Black holes in“normal”
galaxies
Galaxy
Black holes in quasars
Chandra deep
field
February 25, 2003
QSO
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Albert Einstein
 “I want to know God's
thoughts...the rest are details.”
 “Imagination is more important
than knowledge. Knowledge is
limited. Imagination encircles
the world.”
 “With fame I become more
and more stupid, which of
“God does not
course is a very common
play dice with
phenomenon.”
the Universe”
February 25, 2003
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Einstein and Relativity
 1905 – Theory of Special Relativity
 Applies to objects at a constant velocity
 Time dilation and length contraction
 Space and time are intertwined
 Matter and energy are equivalent
 1916 – Theory of General Relativity

Applies to objects that are accelerated

Describes the effects of gravity on spacetime
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Einstein’s equation
Gab = 8 p G Tab
c2
where Gab describes the geometry of
spacetime
and Tab describes the flow of energy and
momentum through spacetime
“Matter tells spacetime how to curve and
spacetime tells matter how to move”
-- J. A. Wheeler
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Solutions to GR equations
 Non-rotating,
spherical black
hole
(Schwarzschild)
 Rotating,
axisymmetric BH
(Kerr)
 Wormholes
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Andrew Hamilton’s BH
Simulator
 Black hole
(Schwarzschild
geometry) with a
simplistic accretion
disk, seen through a
telescope. The disk,
actually a ring, is at the
innermost stable
circular orbit, colored
according to the
redshift. Notice the
multiple images of the
accretion disk.
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Andrew Hamilton’s black
hole simulator
 In orbit around a
Schwarzschild
black hole, shooting
simple cubes at it.
The probes appear
correctly lensed,
redshifted, and
time-delayed.
Some probes are
still en route to the
black hole, while
others, the red
ones, appear
frozen at the
horizon.
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Hamilton’s black hole
trajectory
 Minimum stable orbit
is at 3 Schwarzschild
radii or 300 km for this
30 Mo black hole
 In order to orbit any
closer, you must fire
thrusters to maintain
forward motion
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Hamilton’s orbiting a black
hole
 Orbiting the
black hole at
close to the
photon
sphere. We
are moving at
almost the
speed of light,
so the
relativistic
beaming
effects are
quite strong.
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Spacetime activity
 Bedsheet, small
balls and heavy
weight
 Try rolling the balls
across the sheet with
and without the
weight
 Can you make a
small ball curve in an
orbit around the
weight?
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Bob Nemiroff’s black hole
movies
 Approaching a
black hole
February 25, 2003
 Circling the black
hole
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Nemiroff’s black hole
movies
 Approaching the
photon sphere
February 25, 2003
 Circling the BH at
the photon sphere
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Hamilton’s Wormhole
 Complete Schwarzschild
geometry consists of a
black hole, a white hole,
and two Universes
connected at their
horizons by a wormhole,
also known as the
Einstein-Rosen bridge
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Hamilton’s charged black
hole passage
 Passing inward through
the inner horizon of a
charged black hole.
The point at the center
of the black disk is an
image of our Universe,
infinitely blueshifted,
and should appear as
an infinitely bright flash
of light. The entire
history of the Universe
passes in that point.
The region around the
black disk also appears
blue-shifted and
brightened.
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Hamilton’s black hole into
white hole
 Passing back through the
inner horizon of a charged
BH, into a white hole. The
point at the center of the
black disk is an infinitely
blueshifted image of our
Universe, that appears as
an infinitely bright flash of
light. The entire future of
the Universe passes in
that point. The point
where we entered the
inner horizon is at the
bottom, and the point
where we are exiting the
horizon is at the center of
the black disk.
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Hamilton’s white hole into
new Universe
 Exiting the white hole into
a new Universe, which
appears as an infinitely
blueshifted, infinitely
bright, point at the center
of the black disk. We see
the entire history of the
new Universe in the point.
The noise texture
continues to show how
gas accreting on to the
black hole in our original
Universe would appear
lensed and redshifted.
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Hamilton’s looking back on
our Universe
 We are now in the new
Universe, looking back
at the white hole from
which we have
emerged. The new
Universe is painted with
the 2MASS Milky Way
image. The view is
redshifted and dimmed
by our motion away from
the white hole. Through
the white hole we see
light from our original
Universe, multiply
imaged.
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Hamilton’s escape from
white hole universe
 If we accelerate back
towards the white hole,
in a frantic attempt to get
back to our own
Universe, we find that
the white hole
spontaneously turns into
a black hole as we
approach it. The
accretion disk has been
turned off for clarity.
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Gravitational Radiation
 General Relativity predicts the existence
of gravitational radiation  waves of
gravity that travel at the speed of light
The strongest signal comes
from two black holes
Black hole mergers in distant
galaxies will test General Relativity
in the extreme
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Laser Interferometric
Gravitational Observatory
LIGO Prototype Detector
Engineering
tests in 2003
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Measuring Black Holes
 Mass and spin of black hole can be measured
from the gravitational radiation patterns
emitted in different situations
Distorted Schwarzschild
black hole
February 25, 2003
Lynn Cominsky - Cosmology A350
Distorted Kerr
black hole
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Colliding Black Holes
 Spiral waveform can be calculated reliably
 Ringdown after merger tells you the mass
 Larger computers needed to predict the actual
collision waveforms
February 25, 2003
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Colliding Black Holes
movie
 Movie shows
the event
horizons
merging as two
black holes
collide to form
one larger
black hole
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Colliding Black Holes
 Movie shows the
movie
blue and yellow
gravitational
waves emitted as
the green event
horizons of two
black holes
collide to form
one larger black
hole
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Laser Interferometer Space
Antenna
Launch 2010+
 BH binaries
 BH collisions
 Galactic binaries
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Image a Black Hole!
HST Image
Close to the event horizon
the peak energy is emitted
in X-rays
M87
0.1 arc sec resolution
MAXIM
0.1 micro arc sec resolution
4-8 m arc sec
Micro-Arcsecond
X-ray Imaging
Mission
February 25, 2003
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MAXIM Concept
32 optics (300  10 cm) held in
phase with 600 m baseline
to give
0.3 micro arc sec
Optics
1 km
34 formation flying spacecraft
10 km
Combiner
spacecraft
500 km
System is
adjustable on
orbit to achieve
larger baselines
February 25, 2003
Black hole image!
Lynn Cominsky - Cosmology A350
Detector
spacecraft
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Stephen Hawking
 “God not only plays dice, he also sometimes
throws the dice where they cannot be seen.”
 “My goal is simple. It is complete understanding
of the universe, why it is as it is and why it exists
at all.”
 “It is not clear that intelligence has any long-term
survival value.”
 Proved that if GR is true and the universe is
expanding, then a singularity existed at the birth
of the universe
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Hawking Radiation
 Hawking radiation results from the formation of virtual
particle pairs near the black hole’s event horizon. The
total energy of the pair, E1 +E2 =0.
 According to quantum mechanics, virtual pairs of
particles are always being created from the vacuum –
they usually annihilate, disappearing back into the
vacuum
 However, if the pair is formed near a black hole, one
particle can become real (E1>0) and escape, while the
other falls into the black hole
 The escaping particle makes Hawking radiation, while
to conserve energy, the particle that falls in has to have
E2<0, which lowers the energy of the black hole, and
eventually causes it to evaporate.
February 25, 2003
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Hawking Radiation
Hawking
radiation from
a very small
black hole
 Hawking predicted
that black holes
should radiate due
to the emission of
charged particles
 Bigger black holes
are colder and
fainter
 Hawking radiation
will eventually lead
to the death of BH at
the end of time
February 25, 2003
Evaporation
of miniblack hole
in a
gamma-ray
burst
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Frame Dragging
 Predicted by Einstein’s theory of
Precessing
top
General Relativity
 Rotating bodies drag space and
time around themselves as they
rotate – like a spinning object
stuck in molasses
 It may have been observed by
RXTE in neutron star and black
hole binaries in oscillations
caused by matter in precessing
accretion disks
February 25, 2003
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Frame Dragging
 Gravity Probe B – to be launched in 2003
 Will test 2 predictions of GR using 4 extremely
accurate gyroscopes
 Measure space-time reference frame of Earth –
gyroscopes will move 6.6 arcseconds per year
 Measure frame dragging of Earth – gyroscopes
will move by 42 milliarcseconds per year
These two
effects are at
right angles to
each other
February 25, 2003
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Frame dragging activity
 Paper plate, honey, peppercorns, food
dye, superball
 What happens when the ball spins?
movie
February 25, 2003
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Web Resources
 Pictures from the Hubble Space Telescope
http://oposite.stsci.edu/pubinfo/pictures.html
 Chris Hillman’s Relativity Page
http://www.math.washington.edu/~hillman/relativity.html
 Andrew Hamilton’s Black Hole Flight Simulator
http://casa.colorado.edu/~ajsh/bhfs/screenshots/
 Stephen Hawking’s Home page
http://www.hawking.org.uk/
 Genzel Group Milky Way BH video
http://www.eso.org/outreach/press-rel/pr-2002/pr-1702.html#vid-02-02
February 25, 2003
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Web Resources
 Rossi X-ray Timing Explorer
http://oposite.stsci.edu/pubinfo/pictures.html
 Gravity Probe B http://einstein.stanford.edu
 Micro-Arcsecond X-ray Imaging Mission
http://maxim.gsfc.nasa.gov
 Laser Interferometric Space Array
http://lisa.nasa.gov
 Bob Nemiroff’s black hole movies
http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html
February 25, 2003
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