1. Super novae fringe benefits

(1) standard candles

distance indicators

What's standard?

mass for carbon ``deflagration'' (type I)

mass for core-collapse (type II)

(2) virtually all heavy elements formed

up to iron: in fusion shells (``onion skin'')

beyond iron: neutron capture during explosion

Primordial Abundance:

- nearly devoid of heavy elements

We are all made of star matter

2. Pulsars

Neutron stars:

- smaller than white dwarfs, and more massive

- densities as high as atomic nuclei themselves

- one giant 'nuclei' -- bound by gravity

- high rotation speed

result of collapse and conservation of angular momentum

- strong magnetic fields

narrow particle beam emanating from magnetic poles

- ``lighthouses:'' don't see in every direction

- spin rates as fast as 1000 times per second!

(surface spinning at 20% of speed of light)

How can they hold together?

3. Beyond neutron star densities

white dwarfs

------------------------- 1.4 M limit

neutron stars

------------------------- 3 M limit ???

black holes

Other possibilities before the inevitable limit: (remember the zoo!)

'quark' stars,

with ever-increasingly massive quarks:

'strange' matter

'charm' matter

'bottom' matter

'top' matter

Basic principle:

Equalize the levels of the Fermi Seas for each type of particle

Introduce a new particle whenever the Fermi Seas get high enough to reach that particle's mass

. . . but ultimately, if mass is large enough, gravity wins:

total collapse to singularity

4. Black holes: new physics

First pass on these concepts:

Special Relativity:

- ``Laws of Motion'' when speeds approach the speed of light

(Recall, the speed of light is finite)

- Becomes Newton's ``Laws of Motion'' when speeds are much less than light speed

General Relativity:

- Space and time thought of together as 4 dimensions

- Reformulates gravity as ``curvature'' in space and time

- Acceleration is when an object resists curvature

- ``Free-fall'' is an inertial frame

Both of the above are ``classical'' theories, i.e. no Quantum Mechanics.

Special Relativity has been incorporated into Quantum Mechanics, but there is currently no theory of Quantum Gravity! (yet)

5. Black holes themselves

Event horizon = Schwarzschild radius

R_S 3 km (M/M)

Where escape velocity = speed of light

Warped space-time produces:

Gravitational redshift (NOT Doppler shift)

Time dilation

Why:

Photon requires energy to escape gravitation field but speed is constant

Define:

E = Energy (of light)
h = is Planck's constant (a conversion factor)
c = speed of light
= wavelength of light
= frequency of light

Then,

E = h c /

As photon tries to escape,

E decreases

increases (redder) gravitational redshift

= 1 / decreases time dilation

At the Event Horizon and within:

- E required to escape is infinite.

- So too is gravitational redshift and time dilation.

Nothing gets out!

But ...

Material falling in is heated by tidal forces.

Before the Event Horizon, such material radiates enormous amounts of energy.

x-ray bursters

gamma-ray bursters ???

active galactic nuclei

(a) There can only be massive stars near the Sun.

(b) The most important stars are low-mass stars.

(c) There must have been at least one generation of stars before the Sun and Solar System were formed.

(d) Massive stars could not have produced this material since they would have destroyed the Sun.

(e) Super-novae today are constantly supplying the Solar System with new heavy elements.

(a) The limiting mass for a black hole would go up.

(b) The limiting mass for a black hole would go down.

(c) The limiting mass for a black hole would stay the same.

(d) There would not be a black hole event horizon.

(e) Time dilation at the event horizon would change.