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"Seeing a Black Hole" The First Image of a Black Hole from the Event
Horizon Telescope
Matthew NewbyTemple University
Department of PhysicsMay 1, 2019
Matthew Newby, Temple University, May 1, 2019 2
● Black Holes – a Background● Techniques to observe M87*● Implications
"Seeing a Black Hole" The First Image of a Black Hole from the Event
Horizon Telescope
Matthew Newby, Temple University, May 1, 2019 4
What is a black hole?
Let vesc
→ c, and the escape velocity is greater than the speed of light → “Black”
Classical escape velocity:
Matthew Newby, Temple University, May 1, 2019 5
Einstein (and Hilbert) Field Equation
In General Relativity
Ricci curvature tensor
Metric tensor
Scalar curvature
Stress-energy tensor
“Solution”(“source” term)
Matthew Newby, Temple University, May 1, 2019 6
Constant rs Schwarzschild Radius:
Schwarzschild Metric
Spherically symmetric, isolated, vacuum solution:
Looks like classical escape velocity!
Matthew Newby, Temple University, May 1, 2019 7
Space-Time Interval
● τ is proper time● t is time measured at infinity (τ
∞)
● r, θ, φ, are Schwarzschild spherical coordinates
(i.e., coordinates as viewed at infinity)
● ds is a path element in spacetime
Matthew Newby, Temple University, May 1, 2019 8
General Relativistic Time Dilation
Allow a photon emitted at r to travel to infinity; in that photon’s rest frame:
Since the frequency of a photon is a proper time interval, this implies that the photon’s frequency (and energy) are lower as it travels away from a spherical mass.
Matthew Newby, Temple University, May 1, 2019 9
The Event Horizon
rs is the “Surface of infinite redshift” or event horizon
https://arxiv.org/abs/1511.06025
The event horizon is the “surface” of a black hole.
(Image simulated using Schwarzschild metric and ray tracing)
Matthew Newby, Temple University, May 1, 2019 10
Some Schwarzschild Radii
Object Mass rs
Proton 1.67 x10-27 kg 2.5 x10-54 m
Football 0.5 kg 7.4 x10-28 m
Earth 6.0 x1024 kg 8.8 x10-3 m
Sun 2.0 x1030 kg 3.0 km
Sgr A* 4.3 x 106 M☉ 17 R☉
M87* 6.5 x109 M☉ 127 AU
Matthew Newby, Temple University, May 1, 2019 11
Space
Time
rs
Light Cones are Warped
“One way” inside of Schwarzschild radius
All paths lead to the singularity
Possible Futures
Possible Futures
Possible Futures
Matthew Newby, Temple University, May 1, 2019 12
Simulation of lensing effect near an event horizon. (Click image for animation)
https://arxiv.org/abs/1511.06025
Warped Space Modifies Trajectories
https://upload.wikimedia.org/wikipedia/commons/2/23/Newton_versus_Schwarzschild_trajectories.gif
Gravitationally lensed Einstein Ring (actual image)
ESA/Hubble/NASA
See also: precession of orbits:
Matthew Newby, Temple University, May 1, 2019 13
Rotating Black Hole: Kerr Metric
Rotating black holes involve two event horizons and an “ergosphere.”
Drags space along with its rotation (“frame dragging”)
Wikimedia commons
“Gargantua,” from the movie Interstellar. Based on rotating black hole simulations.
Matthew Newby, Temple University, May 1, 2019 14
Information and Evaporation
Thermodynamic Considerations imply that Black Holes should be able to radiate.
- Frozen Stars: Redshifted imprint of original collapse- Unruh Effect: Relativistic temperatures- Hawking Radiation: pair creation/annihilation
No-Hair Theorem: Black holes destroy all infalling information except for:
- Mass/Energy- Angular Momentum- Electric Charge
Solutions to some of these considerations involve “fuzzy” event horizons, or create incompatibilities between particle physics and general relativity.
Matthew Newby, Temple University, May 1, 2019 15
Laboratories for Extreme Physics
Very importantly:
The event horizon of a black hole is not only a test of General Relativity, but also of how General Relativity, Quantum Physics, and Thermodynamics come together in an extreme situation.
New physics may reveal itself here.
Matthew Newby, Temple University, May 1, 2019 16
Known Black Holes
Black Holes have been detected through:
- X-ray Binaries (Cygnus X-1)- Companion Orbits (Sgr A*)- Active Galactic Nuclei (M87*)- Gravity Wave Detections (LIGO/VIRGO)- Direct Radio Imaging (EHT)
Matthew Newby, Temple University, May 1, 2019 17
Stellar-mass BHs:3-15 M☉
Form from exploding high-mass stars.
Supermassive BHs:105+ M☉
Form alongside galaxy formation.
Intermediate-mass BHs:Formation unknown!
Primordial BHs:Formed with Big Bang, maybe intermediate-mass?
Black Hole Masses
Matthew Newby, Temple University, May 1, 2019 18
The Event Horizon Telescope
Wavelength 1.3 mm (microwave)
Angular Resolution 35 micro arcseconds
Mass of M87* 6.5 x109 M☉
Distance to M87* 53.5 Mly
Gas accretion rate of M87* 90 Earth masses/day
Apparent velocity of relativistic jet
4 to 6 c
Quick Facts:
Matthew Newby, Temple University, May 1, 2019 19
Interferometry
Very Long Baseline Interferometry (VLBI) [Credit: EHT]
Matthew Newby, Temple University, May 1, 2019 21
Big Data
Statistical reconstruction of wave data (Image: Katie Bouman, EHT)
Petabytes of data – too much for the internet!
(https://www.nsf.gov/news/special_reports/blackholes/downloads/data_infographic.jpg)
Matthew Newby, Temple University, May 1, 2019 23
M87*
Accretion Disk
“Shadow”
Relativistic Brightening
Relativistic Dimming
Rotation Direction
Matthew Newby, Temple University, May 1, 2019 24
M87* Time Series
Shows changes with time.
More importantly, shows image is from a stable source (and not random noise)
Matthew Newby, Temple University, May 1, 2019 25
Summary: Science Products
● Test of Schwarzschild metric
● Test of General Relativity
● Test of interplay between quantum mechanics and relativity
● High energy gas physics (accretion disk dynamics)
● Jet creation
● Details of active galactic nuclei action
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