Quarks to Cosmos Lecture Sheet 12

Novae, Supernovae, Heavy Stars

What is needed for a nova?

White dwarf + mass transfer.

What is a Roche lobe?

Region where a star’s gravity dominates; overflow → accretion.

Chandrasekhar limit?~1.4 solar masses.

What happens if a white dwarf exceeds it?

Type Ia supernova.

Heavy vs light star evolution?

Heavy: fuse to iron; light: stop at C/O (limit ~8 solar masses).

What accumulates in heavy star cores?

Iron.

Nova vs supernova?

Nova = surface explosion; supernova = catastrophic collapse.

Type I vs Type II supernova?

Type I: no H lines; Type II: hydrogen present.

What stops core collapse supernova?

Neutron degeneracy pressure.

Most stable element?

Iron-56.

Alpha, beta, neutron decay?

Alpha = He nucleus; Beta = n ↔ p + e ± ν; Neutron = free neutron emitted.

s-process?

Slow neutron capture; stops at Pb; AGB stars.

r-process?

Rapid neutron capture; creates very heavy elements; mergers & supernovae.

Remnants of Type Ia and Type II?

Type Ia: none; Type II: neutron star or black hole.

Neutron star properties?~10 km radius, 1.4–2 M☉, ~10^17 kg/m³.