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Black Holes. • Regions of space from which nothing, not even light, can escape because gravity is so strong. • First postulated in 1783 by John Michell • Term “black hole” coined in 1969 • Observational evidence starting in 1970s. We see the effects a black hole has on matter and radiation

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black holes
Black Holes

• Regions of space from which nothing, not even light,

can escape because gravity is so strong.

• First postulated in 1783 by John Michell

• Term “black hole” coined in 1969

• Observational evidence starting in 1970s

We see the effects a

black hole has on matter and radiation

near it; we have not yet seen

a black hole directly.

black hole structure

Schwarzschild BH

Black Hole Structure
  • Schwarzschild radius defines the event horizon
  • Rsch = 2GM/c2
  • Singularity is “clothed” inside the event horizon
  • Cosmic censorship prevails (you cannot see inside the event horizon)
what is this
What is This?

• Diagram of the effect of gravity

(gravitational potential well)

near the black hole on the fabric

of spacetime

• It is a 2-D depiction of a 3-D


types of black holes
Types of Black Holes
  • Primordial – can be any size, including very small (If <1014 g, they would still exist)
  • Stellar Mass – must be at least 3 solar masses(~1034 g)
  • Intermediate Mass – a few thousand to a few tens of thousands of solar masses; possibly the agglomeration of stellar mass holes
  • Supermassive – millions to billions of solar masses; located in the centers of galaxies
the first first black hole
The First “First” Black Hole
  • Cygnus X-1 binary system
  • Most likely mass is 16 (+/- 5) Mo
  • Mass determined by Doppler shift measurements of optical lines
ngc 4261
NGC 4261
  • 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
supermassive black holes
Supermassive Black Holes
  • Rotating black hole in the center of a galaxy, which is emitting relativistic jets of material
  • Emission is from just outside the event horizon
active galaxies
Active Galaxies

Jets of fast moving particles

and gamma-rays

Disk of galaxy with

supermassive blackhole in center

Halo of gas, and dust

Quasars, Blazars, Seyferts, AGN, ….etc, etc, etc

black holes are everywhere

Chandra deep field

Black Holes Are Everywhere!

Black holes in empty space

Deep Image


Black holes in“normal” galaxies


Black holes in quasars


galactic black hole
Galactic Black Hole
  • Zooms in to show the region surrounding the black hole in the center of a galaxy
  • Accretion disk of gas swirls around black hole
galactic black holes
Galactic Black Holes
  • NGC 3377 & NGC 4486b are 2.7 arc-sec images
  • NGC 3379 is 5.4 arc seconds
  • Note double nucleus in central 0.5 arc-sec of NGC 4486b
colliding bhs
Colliding BHs
  • Spiral waveform can be calculated reliably
  • Ringdown after merger tells you the mass
  • Larger computers needed to predict the actual collision waveforms
gamma ray bursts
Gamma-ray Bursts!
  • Most powerful explosions in the Universe today - and one of the greatest mysteries of modern astrophysics
  • “When you see a gamma-ray burst, a black hole is being born” – M. Livio
gamma ray astronomy

Gamma-ray Astronomy

(The Short, Short Story…)

sources of g ray emission
Sources of g-ray Emission

• Black holes

• Active Galaxies

• Pulsars

• Gamma-ray bursts

• Diffuse emission

• Supernovae

• Unidentified

grbs the very brief version
GRBs: The Very Brief Version
  • • Humble Beginnings: A Bomb or Not a Bomb?
    • Vela Program
  • • A few hundred events, a few hundred theories
  • • Finally, science to the rescue
    • Compton Gamma Ray Observatory
    • BeppoSAX/ROTSE/HST/ (and a host of others)
models for grbs
Models for GRBs


Merging Neutron Stars

what s next
What’s Next
  • New Missions = Better Data
  • Improved theory
  • Serendipity
new missions better data
New Missions = Better Data

HETE II (launched 7 October 2000)


Swift (2003)

GLAST (2005)


imagine we have detected a grb
Imagine…we have detected a GRB!

Our gamma-ray detector measures 5.27 x 10 -6 ergs/cm2

Hey, Laura!

What’s so impressive about that?!??!!!

wrapping up the universe
Wrapping Up the Universe
  • The light we measure decreases as a function of distance,
  • We can find a galaxy’s distance if we can measure its velocity from its redshift,
  • By measuring the distances of gamma-ray bursts from their redshifts, we can see how amazingly powerful these events are.
remember the falloff of light
Remember the Falloff of Light

What was emitted

What you detect =


4 p D

remember hubble s law
Remember Hubble’s Law

v = Ho * d

Ho is called the Hubble constant. It is generally

believed to be around 65 km/sec/Mpc.

and now for a real spectrum
And Now for a Real Spectrum...

This is an optical spectrum of a GRB from Keck, the

world’s largest optical telescope. The locations of

several Doppler shifted spectral lines are shown.

a big hint from redshift to power
A BIG Hint: From Redshift to Power

Step-by-step power calculation:

1. Measure the redshift of three spectral lines

2. Take the average redshift, z

3. From this, calculate the velocity v=z*c

4. Using the Hubble Constant, get the distance


5. Convert distance in Mpc to distance in cm

6. Now, with the distance to the GRB, and the

value measured at our detector, calculate

power: P=4πd2*measured flux


Needed Information

1 Mpc ~ 3 x 10 19 km

L = 5.3 x 10-6 ergs/cm2



are the most

Powerful Explosions

in the Universe!