Black Holes Regions of space from which nothing, not even ligh an 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.
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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.
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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 ablack hole has on matter and radiation
near it; we have not yet seena black hole directly.
Journey to a Black Hole
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Black Hole Structure
Schwarzschild radius defines the event horizon
Rsch = 2GM/c2
Singularity is “clothed” inside the event horizonCosmic censorship prevails (you cannot see inside the event horizon) Schwarzschild BH
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-Devent
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 HoleCygnus X-1 binary systemMost likely mass is 16 (+/- 5) Mo
Mass determined by Doppler shift measurements of optical lines
NGC 4261
100 million light years away
1.2 billion Mo black hole in a region the size of our Solar SystemMass of disk is 100,000 Mo
Disk is 800 light years across
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
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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
Radio & Optical Image of an AGN
NGC 4261
Deep Image
Black Holes Are Everywhere!
Black holes in quasars
QSO
Galaxy
Empty
Black holes in“normal” galaxies
Black holes in empty space
Chandra deep field
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
NGC 3377 & NGC 4486b are 2.7 arc-sec imagesNGC 3379 is 5.4 arc seconds Note double nucleus in central 0.5 arc-sec of NGC 4486b
Colliding BHsSpiral waveform can be calculated reliablyRingdown after merger tells you the massLarger computers needed to predict the actual collision waveforms
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(The Short, Short Story…)
Sources of -ray Emission
• Black holes• Active Galaxies• Pulsars• Gamma-ray bursts• Diffuse emission• Supernovae• Unidentified
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)
Vela Program
CGRO
Gamma-Ray Bursts
Distribution of GRBs in the Sky
What BeppoSAX Saw
What HST Saw (Much Later)
Breakthrough!
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Models for GRBs
HypernovaMerging Neutron Stars
Come On…Let’s Vogue
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What’s Next
New Missions = Better Data
Improved theory
Serendipity
New Missions = Better Data
Swift (2003) GLAST (2005)
HETE II (launched 7 October 2000) INTEGRAL (2001)
Swift
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
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
What you detect =
What was emitted
4 D2
Remember Hubble’s Law
v = Ho * d Ho is called the Hubble constant. It is generally believed to be around 65 km/sec/Mpc.
Remember the Doppler Shift
=
vc
=z =
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 Little Musical Interlude
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A BIG Hint: From Redshift to Power
Step-by-step power calculation:
1. Measure the redshift of three spectral lines2. Take the average redshift, z3. From this, calculate the velocity v=z*c4. Using the Hubble Constant, get the distance
d=v/Ho
5. Convert distance in Mpc to distance in cm6. Now, with the distance to the GRB, and the
value measured at our detector, calculate power: P=4πd2*measured flux