PX158 - I7b - neutron stars

the chandrashekhar limit for a white dwarf is $\sim 1.4M_{\odot }$

electrons are fused with the nuclei of atoms, only neutrons are packed together

$R_{NS}\approx 10km$, $M_{NS}\approx 1.4M_{\odot }$, and ${\rho }_{NS}={10}^{18}kg{m}^{-3}$, $g=2\times {10}^{12}m{s}^{-2}$

a drop of one meter$\to 2000km{s}^{-1}$

from infinity$\to 200000km{s}^{-1}=\frac{2}{3}c$

from a $1mm$ hill$\to$ human lifetime worth of energy

due to the high $g$, they are very smooth

spin very rapidly $\sim 700rev/s$

very strong magnetic field $\sim {10}^{10}T$

$B$-field can be misaligned to the rotation axis

this gives rise to 'pulsars', which were originally known as 'little green men' (LGM) as they were thought of as aliens

pulsars have shown:

• exoplanets around neutron stars
• test predictions of general relativity (gravitational waves)