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Black Holes The Science Behind The Science Fiction. Eliot Quataert (Berkeley Astronomy Dept). Science Fiction. “A Journey That Begins Where Everything Ends”. “Infinite Space, Infinite Terror”. A Muse for Popular Culture. The Far Side. The giant Schilling vortex has

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black holes the science behind the science fiction

Black HolesThe Science Behind The Science Fiction

Eliot Quataert (Berkeley Astronomy Dept)

science fiction
Science Fiction

“A Journey That Begins

Where Everything Ends”

“Infinite Space,

Infinite Terror”

a muse for popular culture
A Muse for Popular Culture

The Far Side

The giant Schilling vortex has

become the black hole of popular

culture, sucking in all images and

sound and allowing only soundbites

about The Great Pitcher’s courage

and legacy to escape.

Angry Yankee’s Fan

Gary Larson

“Suddenly, through forces not yet fully understood, Darren Belsky’s apartment became the center of a new black hole”

slide5
What is a black hole?
  • Do BHs exist in Nature?
    • YES!
  • How do we find them?
  • What do they look like?
eluding gravity s grasp
Eluding Gravity’s Grasp

Escape Velocity

Escape Velocity

Speed Needed To

Escape An Object’s

Gravitational Pull

Mass M

Radius R

Earth: Vesc = 27,000 miles/hour (11 km/s)

Sun: Vesc = 1.4 million miles/hour (600 km/s)

dark stars rev john michell 1783 pierre simon laplace 1796
“Dark Stars”Rev. John Michell (1783) & Pierre-Simon Laplace (1796)

Speed of light  1 billion miles/hour (3x105 km/s)

  • What if a star were so small, escape speed > speed of light?

A star we couldn’t see!

Earth mass: R  1 inch

Solar mass: R  2 miles

Vesc = speed

of light 

slide9

1915: General Relativity, Einstein’s Theory of Gravity 1916: Schwarzschild’s Discovery of BHs in GRBHs only understood & accepted in the 1960s (Term “Black Hole” coined by John Wheeler in 1967)

Albert Einstein

Karl Schwarzschild

slide10

Black Holes in GR

If an object is small enough, gravity overwhelms pressure and the object collapses. Gravity is so strong that nothing, not even light, can escape.

“Radius” of a BH

 2 miles for a solar mass

 1 inch for an Earth mass

NOT a solid surface

All Mass at the Center (GR not valid there)

dispelling the myths
Dispelling the Myths …
  • BHs are not cosmic vacuum

cleaners:only inside the horizon

is matter pulled inexorably inward

  • Far away from a BH, gravity

isno differentthan for any

other object with the same mass

  • If a BH were to replace the sun, the orbits of planets, asteroids, moons, etc., would beunchanged

(though it would get really really cold).

how do we find bhs in nature
How do we find BHs in Nature?

Sidney Harris

“It’s black, and it looks like a hole.

I’d say it’s a black hole.”

where are bhs found
Where are BHs Found?

Centers of Galaxies

Binary Stars

1 BIG BH per galaxy

million-billionx mass of sun

formation not fully understood

millions of ‘little’ BHs per galaxy

~ 10 x mass of sun

formed by collapse of a massive star

shedding light on bhs x ray binaries
Shedding Light on BHs: X-ray Binaries

Gas falling into a BH gets very hot and emits lots of radiation in X-rays

Accretion is how we “see” a black hole

Matsuda

If two stars orbit close enough to each other, mass gets pulled from one and falls (accretes) onto the other. The smaller the target object, the faster the gas moves and the hotter it gets.

how do we know it s a bh
How do we know it’s a BH?
  • Nature is tricky: couldn’t it be another “small star” like a neutron star or a white dwarf?
  • Measure mass of “X-ray star” by motion of its companion (a star like the sun)
how do we know it s a bh1
How do we know it’s a BH?
  • Nature is tricky: couldn’t it be another “small star” like a neutron star or a white dwarf?
  • Measure mass of “X-ray star” by motion of its companion (a star like the sun)

Mass > 3 solar

masses  BH!

  • Roughly a dozen BHs found this way (tip of the iceberg)

Chandrasekhar

where are bhs found1
Where are BHs Found?

Centers of Galaxies

Binary Stars

1 BIG BH per galaxy

million-billionx mass of sun

unclear how they form

millions of ‘little’ BHs per galaxy

~ 10 x mass of sun

formed by collapse of a massive star

the milky way galaxy 100 000 light years across
The Milky Way Galaxy: ~ 100,000 light-years across

Scale: Size of Solar System: 0.01 light-years

Typical Distance btw. Stars: 1 light-year

4 106 Msun

Black Hole

Central Black Hole Mass: 4 millionMsun

Also ~ millions of 10 Msun BHs

evidence for a big bh at the center of our galaxy
Evidence for a Big BH at the center of our Galaxy

Motion of stars

at the center

of the Milky

Way over the

past decade

Genzel et al; also Ghez et al.

10 light-days  size of solar system

evidence for a big bh at the center of our galaxy1
Evidence for a Big BH at the center of our Galaxy

Velocities & Orbits

of Stars  Mass

BH in our Galaxy

weighs in at

4 MILLION SOLAR MASSES

Genzel et al; also Ghez et al.

10 light-days  size of solar system

light from gas falling into the black hole
Light From Gas Falling Into the Black Hole

BH

Infrared Image

X-ray Image

Analogy: Solar Flare

many varieties of massive bhs
Many Varieties of Massive BHs

Our

Galaxy

Brightness of Central Black Hole

active galactic nuclei
“Active Galactic Nuclei”

radio image

The BH ejects beams (“jets”) of

matter & energy far outside its host

galaxy into the surrounding universe

The BH can outshine all of

the stars in its host galaxy!

the moral of the story
The Moral of the Story …
  • Physicists said that Black Holes could exist
    • the ultimate victory of gravity over all other forces
  • Astronomers find that BHs do exist
    • 1 Big BH per galaxy (~ million-billion solar masses)
    • millions of little BHs per galaxy ( ~ solar mass)
  • BHs are responsible for the most dramatic and energetic phenomena in the universe
    • BHs are “seen” via the light produced by infalling gas & via the gravitational pull that they exert on nearby objects