Neutron stars and beyond

There it is!

Cassiopeia A…the remnant of the supernova of 1680

How many pulsars (neutron stars) are there in the sky?

http://www.atnf.csiro.au/research/pulsar/psrcat

Neutron stars: from exotica to numerous astronomical objects

A final mystery…pulsar

masses are nearly all AT the Chandrasekhar

Limit

Neutron Stars – Extreme Objects

Does it get any weirder?

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

What happensHere?

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

Black Holes in classical physics: Given a mass M, how compact (squished) does it

have to be?

Schwarzschild Radius

Rs = 2GMc2

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?

General Relativity and Black Holes

General Relativity: a theory of gravity

Basic mathematical object: 4 dimensional spacetime

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

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

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?

They do exist, in two types

Little Ones……and……

……Big Ones