1. Black Holes: physics and astronomy

2. Black Holes in classical physics: Given a mass M, how compact (squished) does it have to be?
Schwarzschild Radius
Rs = 2GM c2

3. General Relativity and Black Holes
General Relativity: a theory of gravity
Basic mathematical object: 4 dimensional spacetime

4. Basic Ingredients of General Relativity
(A) Objects move between 2 points in spacetime on the shortest path between those points (geodesics)
(B) The presence of mass warps or bends spacetime
The Einstein Field Equations

5. General Relativistic Black Holes
For sufficient concentration of mass in sufficiently small region, there is a rip or hole poked in spacetime
Schwarzschild Radius
DEMO with analogs

6. Question: Do black holes exist in nature?
What would you look for? What kind of observation would reveal a black hole?

7. Cygnus X-1: the prototype black hole
Artists’s conception of Cygnus X-1

8. Where Cygnus X-1 is located

9. An example of a black hole system
Black hole and a red dwarf

10. A key to black holes: hot accretion disks

11. Present knowledge about black holes
20 confirmed black hole systems
Least massive: solar masses
Most massive: solar masses
Remember all pulsars have 1.4 solar masses

12. Black holes on larger scales: the center of the Milky Way
A black hole of 2.5 million solar masses, and more to come