1. Lecture 28- Black Holes But first, today’s picture of the day
Picture of the Sun
XX Trianguli with starspots

2. Neutron Stars – Extreme Objects
Does it get any weirder?

3. Basic physics suggests a way: the maximum mass of a neutron star

4. Black Holes in Theory: you check in, but you don’t check out
Theoretical ways of describing them
(A) Classical physics: an object with escape speed greater than the speed of light (> c)
(B) General Relativity and Black Holes

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

6. Cramming something inside the Scharzschild Radius extreme matter
Example: Planet Earth
M= 5.97E+24 kilograms
Rs = 9E-03 meters = 0.9cm !!!!
DEMO
But always ask: do they exist?

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

8. 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

9. 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

10. But do they exist? Is nature capable of producing such strange objects?
Question: what kind of astronomical objects, with what kind of quantitative properties, would you look for?

11. They do exist, in two types
Little Ones……and……

12. ……Big Ones