"Seeing a " The First Image of a Black Hole from the

Matthew Newby Temple University Department of Physics May 1, 2019 "Seeing a Black Hole" The First Image of a Black Hole from the Event Horizon Telescope

● Black Holes – a Background ● Techniques to observe M87* ● Implications

Matthew Newby, Temple University, May 1, 2019 2 "Seeing a Black Hole"

Matthew Newby, Temple University, May 1, 2019 3 What is a black hole?

Classical escape velocity:

Let vesc → c, and the escape velocity is greater than the speed of light → “Black”

Matthew Newby, Temple University, May 1, 2019 4 In

Einstein (and Hilbert) Field Equation

Metric tensor Stress-energy tensor Ricci curvature tensor Scalar curvature

“Solution” (“source” term)

Matthew Newby, Temple University, May 1, 2019 5 Schwarzschild Metric

Spherically symmetric, isolated, vacuum solution:

Constant rs Schwarzschild Radius:

Looks like classical escape velocity!

Matthew Newby, Temple University, May 1, 2019 6 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 7 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 8 The Event Horizon

rs is the “Surface of infinite redshift” or event horizon

The event horizon is the “surface” of a black hole.

(Image simulated using Schwarzschild metric and ray tracing)

https://arxiv.org/abs/ 1511.06025

Matthew Newby, Temple University, May 1, 2019 9 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

6 Sgr A* 4.3 x 10 M☉ 17 R☉

9 M87* 6.5 x10 M☉ 127 AU

Matthew Newby, Temple University, May 1, 2019 10 Light Cones are Warped

“One way” inside of Schwarzschild radius

All paths lead to the singularity

Time

Possib Po Possible le F ss Futur ut ib Futures es ur le es

Space

rs

Matthew Newby, Temple University, May 1, 2019 11 Warped Space Modifies Trajectories

Simulation of lensing effect near an Gravitationally lensed Einstein Ring event horizon. (Click image for (actual image) animation) ESA/Hubble/NASA https://arxiv.org/abs/1511.06025 See also: precession of orbits: https://upload.wikimedia.org/wikipedia/commons/2/23/Newton_versus_Schwarzschild_trajectories.gif Matthew Newby, Temple University, May 1, 2019 12 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 13 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 14 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 15 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 16 Black Hole Masses Stellar-mass BHs:

3-15 M☉ Form from exploding high-mass stars.

Supermassive BHs: 5 10 + M☉ Form alongside galaxy formation.

Intermediate-mass BHs: Formation unknown!

Primordial BHs: Formed with Big Bang, maybe intermediate- mass?

Matthew Newby, Temple University, May 1, 2019 17 The Event Horizon Telescope

Quick Facts:

Wavelength 1.3 mm (microwave)

Angular Resolution 35 micro arcseconds

9 Mass of M87* 6.5 x10 M☉

Distance to M87* 53.5 Mly

Gas accretion rate of M87* 90 Earth masses/day

Apparent velocity of relativistic 4 to 6 c jet

Matthew Newby, Temple University, May 1, 2019 18 Interferometry

Very Long Baseline Interferometry (VLBI) [Credit: EHT]

Matthew Newby, Temple University, May 1, 2019 19 Very Long Baseline

Matthew Newby, Temple University, May 1, 2019 20 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 21 Target: M87*

Matthew Newby, Temple University, May 1, 2019 22 M87*

Relativistic Dimming Rotation Direction “Shadow”

Accretion Disk Relativistic Brightening

Matthew Newby, Temple University, May 1, 2019 23 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 24 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

Matthew Newby, Temple University, May 1, 2019 25