Post on 14-Apr-2018
transcript
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 1/40
Black Holes The Science Behind The Science Fiction
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 2/40
• What is a black
hole?
• Do BHs exist inNature?
–YES!
• How do we find them?• What do they look
like?
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 3/40
Stars
Pressure Balances Gravity
The Sun
F r o m w w w . a s t r o n o m y n o t e s . c o m
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 4/40
Eluding Gravity’s Grasp
Earth: Vesc = 27,000 miles/hour (11 km/s)
Sun: Vesc = 1.4 million miles/hour (600 km/s)
V esc
2GM
R
Mass M
Radius R
Escape Velocity
Escape Velocity
Speed Needed To
Escape An Object’s
Gravitational Pull
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 5/40
“Dark Stars”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
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 6/40
1915: General Relativity, Einstein’s Theory of Gravity
1916: Schwarzschild’s Discovery of BHs in GR
BHs only understood & accepted in the 1960s
(Term “Black Hole” coined by John Wheeler in 1967)
Karl SchwarzschildAlbert Einstein
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 7/40
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)
Black Holes in GR
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 8/40
Gravity bends the path of light
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 9/40
Massive bodies and escape speed
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 10/40
Gravity bends the path of light
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 11/40
.Mass
.Total electric charge
.Spin = angular momentum
Three parameters completely
describe the structure of a black hole
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 12/40
Seeing black holes
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 13/40
Gravitational lensing
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 14/40
Basic structure of black hole..
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 15/40
Event horizon
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 16/40
Rotating black holes
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 17/40
A nonrotating black hole has only a “center”
and a “surface”
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 18/40
Intro: Of fourth dimension
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 19/40
mass bends space-time
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 20/40
Falling into a black holes
• Signals time dilated and red
shifted . (external)
• No communication
• Incoming signals can enter
• Fall for a finite time in event
horizon
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 21/40
Falling into a black hole
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 22/40
Gravitational redshift
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 23/40
Falling into a black hole
• Spaghettification
Ripped apart
• Atoms
• Electrons
nuclei
• Protons• Neutrons
Quarks
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 24/40
How do we find BHs in Nature?
“It’s black, and it looks like a hole.
I’d say it’s a black hole.”
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 25/40
Where are BHs Found?
Centers of Galaxies Binary Stars
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 26/40
The Milky Way Galaxy: ~ 100,000 light-years across
4 106 Msun
Black Hole
Scale: Size of Solar System: 0.01 light-years
Typical Distance btw. Stars: 1 light-year
Central Black Hole Mass: 4 million Msun
Also ~ millions of 10 Msun BHs
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 27/40
Stars in the Central
Light-Year of the Galaxy
Keep Zooming In …
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 28/40
Milky Way
Black Holes and Galaxies:
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 29/40
• A striking
correlation wasfound between
black holes
and their host
galaxies.
• 0.1%
•Directly
proportional
Black Holes and Galaxies:
Chicken or Egg?
Techniques for finding black holes
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 30/40
Techniques for finding black holes
•Accretion disks
•
Gas jets•Xray images
•Infrared images
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 31/40
Seeing black holes
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 32/40
Light From Gas Falling
Into the Black Hole
Infrared Image
BH
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 33/40
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 34/40
How do black holes forms ?
•Gravitational collapse
•Emerge due toattraction
•Big bang
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 35/40
These are some of supernova
explosion
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 36/40
36 Dr. H. Fearn CSUF Physics
How do big Black Holes form
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 37/40
Dispelling the Myths …
• BHs are not cosmic vacuumcleaners: only inside the horizon
is matter pulled extremely inward
• Far away from a BH, gravity
is no different than for any
other object with the same mass
M87
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 38/40
Look closer
still:
Disk of gas
orbiting at500 km/sec,
around
one billion
solar massescrammed into
1 parsec.
A black hole.
M87
C A
7/30/2019 Black Holes Ultimate211
http://slidepdf.com/reader/full/black-holes-ultimate211 39/40
Jets from atiny region in
the center
power
tremendousluminosity in
radio and X
rays.
A black hole.
Cen A