What happens to the collapsing core?
• Neutron star (more in next chapter)
– Quantum rules also resist neutron packing
• Densities much higher than white dwarfs allowed
– R ~ 5 km      ~ 1014 gm/cm3   (similar to nucleus)
• M limit uncertain,  ~2 or ~3 MSun before it collapses
– Spins very fast (by conservation of angular
– Trapped spinning magnetic field makes it:
• Act like a “lighthouse” beaming out E-M radiation (radio,
– pulsars
• Accelerates nearby charged particles