Neutron Stars 1: Basics. Andreas Reisenegger ESO Visiting Scientist Associate Professor, Pontificia Universidad Católica de Chile. Outline of the Lecture Series. Basics: Theory & history: prediction, discovery, etc.
Neutron Stars 1: Basics
ESO Visiting Scientist
Pontificia Universidad Católica
Ground state (T=0) has all particles in the orbitals of the lowest possible energy
Fermi sphere in momentum space:
Each orbital has a phase-space volume
Ground state of system of N fermions of spin ½ (sz = ½) in a spatial volume V
Combining with hydrost. equil. unique mass
1932: James Chadwick discovers the neutron.
Baade & Zwicky (1934):
“With all reserve we advance the view that supernovae represent the transition from ordinary stars into neutron stars, which in their final stage consist of extremely closely packed neutrons.”
Supernova 1987A (23 Febr. 1987) in the Large Magellanic Cloud:
before & after
Collapse of stellar core
huge density forces p + e n +
Neutrinos ()escape: a few detected 2 hours before the light of SN 1987A.
BUT:No neutron star found!
Mass reduction ~ 20% when NS forms (carried away by neutrinos, perhaps gravitational waves)
Since P=P() only (no dependence on T, equilibriumcomposition),
these two equations are enough to calculate the NS or WD structure.
dL/dr=..., dT/dr=... are important only for the thermal evolution.
First (numerical) solution for NSs: Oppenheimer & Volkoff 1939
The state of matter changes with density (T 0):
Black (green) curves are for normal matter (SQM) equations of state.
Regions excluded by general relativity (GR), causality, and rotation constraints are indicated.
Contours of radiation radii R are given by the orange curves.
The dashed line labeled I/I = 0.014 is a radius limit estimated from Vela pulsar glitches (27).
from Lattimer & Prakash 2004
1967: PhD student Jocelyn Bell & her supervisor Anthony Hewish detect a very regular Pulsating Source of Radio (PSR 1919+21)with P=1.377 s, initially “LGM 1”.
Pulsar in the Crab nebula
(remnant of SN 1054)
Fig. by I. Stairs,
Several other classes of observed objects are also believed to be NSs:
See tomorrow’s Lecture for details...