supernovae and neutron stars

Supernovae and Neutron Stars

Specific textbook sections

• Evolution after the main sequence: Section 19.4

• White dwarf stars: Section 20.1

• Supernovae and neutron stars: Section 20.2

Core collapse of a massive star has two consequences

• Massive explosion (1044 Joules)

• Production of a neutron star

Formation of a neutron star from stellar core

• As core collapses, matter becomes compressed

• Electrons and protons forced together e+p > n + nu (neutronization)

• Core of the becomes a neutron fluid• Neutronization produces a burst of neutrinos• Neutron fluid in core becomes degenerate

and rigid

The physics of a self-gravitating neutron blob (neutron star)

• Radius versus mass relation for neutron star

• Notice size of neutron star

• Masses extend above Chandrasekhar limit

Theoretical prediction of the existence of a neutron star

• The remnant after the explosion of a massive star

• An object having the mass of the Sun (or more) but in an object with the diameter of Iowa City!

• An equivalent to the Chandrasekhar mass (largest possible mass of a neutron star)

• Do they exist?

The problem of the Crab Nebula…the remnant of the supernova of 1054 AD

Even today,something is powering the Crab Nebula, causing it to shine at x-rays

1968: The Discovery of Pulsars: Rotating Neutron Stars

http://www.jb.man.ac.uk/~pulsar/Education/Sounds/sounds.html

Pulsar properties

• Highly regular pulse properties

• PSR0329+54, P=0.714519699726 sec

• PSR1633+24, P=0.4905065128003 sec

• What in nature could provide such a perfect clock?

• Demo

Pulsars as rotating neutron stars

demo

The Crab Nebula Pulsar

http://chandra.harvard.edu/photo/2002/0052/movies.html

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 Chandrasekh

ar Limit

Periods and Period Derivatives for Pulsars