Download 31 October: 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.h
tml
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…pul
sar masses
are nearly all
AT the
Chandrasekh
ar Limit
Periods and Period Derivatives for Pulsars